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Bosch Amborola (Model 16)
10/27/2009 1:06:10 PMMike Basciano
Hello,

I have what I believe to be a Bosch Amborola Model 16 that was once my grandfathers. It used to sit on his bedroom dresser and I remember it being there ever since I was little. When he passed, it was given to me. As I know very little about antique radios, I am looking for some help on how to get it running. I do have somewhat of a technical background, but am certainly not a radio repairman.

I understand from some research that this is a battery powered model. Can I assume that I could use a regulated DC power supply to power up the radio? If so, what is the correct voltage/amperage of the power supply?

One of the 6 tubes is missing. It is the one on the far right as viewed from the top of the unit (facing the front). As I cannot find any literature that actually calls out what each tube number is, I have no way to tell what tube is needed to replace the missing one. Does anyone have a list of the tube numbers that are needed to make the unit work properly?

Lastly, I am assuming that the unit requires an external speaker, which I do not have. What would be an era appropriate speaker that would have gone with this unit back in the 1920's or 30's?

Thank you very much for anyone's assistance.

Regards,

Mike B.

10/27/2009 1:17:34 PMWarren
A schematic is shown here.

http://www.nostalgiaair.org/Resources/763/M0040763.htm

As you can see, it is going to need more than just one single voltage supply.

10/27/2009 1:22:13 PMMike B
:A schematic is shown here.
:
:http://www.nostalgiaair.org/Resources/763/M0040763.htm
:
:As you can see, it is going to need more than just one single voltage supply.
:
Warren,

Thank you for the link. I did find this schematic but was unclear on what the actual tube numbers were. If I am not mistaken, there is a small "box" that shows what I thought were the tubes on this model. They numbers are: 3AF, 2AF, 1RF, 2RF, DET & 1AF. Are these the actual tube numbers that I would need, particularly the missing one, 1AF?

Also, when you state that I will need more than a single power supply, what exactly do you mean?

Sorry if I sound ignorant...

Thank you.

Mike B

10/27/2009 1:42:00 PMWarren
All the tubes are 01A

http://www.nj7p.org/Tube4.php?tube=01a

The power supply, has voltages for the tube filaments (A)
Then there are other voltages for the B+ and grid bias supply.

10/27/2009 1:45:44 PMMike B
:All the tubes are 01A
:
:http://www.nj7p.org/Tube4.php?tube=01a
:
:The power supply, has voltages for the tube filaments (A)
:Then there are other voltages for the B+ and grid bias supply.
:
10/27/2009 1:48:07 PMWarren
Yes
10/27/2009 1:51:31 PMMike B
:Yes
:
NICE! Thank you! I am on a mission to get some tubes now. Thank you very much for the help!
10/27/2009 3:04:43 PMGeorge....need a few tubes Mike?
Mike ...I have this exact same set...with a LARGE Bosch cone speaker. I Bought the set at an auction and someone had put a modern power supply VERY neatly inside the set..UNDER THE CAHSSIS!!! I removed it and mounted it in a small plastic tool box. The only thing I did to my set was replace the cable with all the wires. Mine was brittle beyond use....I Also believe that this was the first set that the Bosch company made...1924-25 If want a few good tubes let me know i could sell you some at a reasonable price. George..I left my email addy

::Yes
::
:
:
:NICE! Thank you! I am on a mission to get some tubes now. Thank you very much for the help!
:

10/27/2009 3:09:06 PMWarren
George. It would be cool of you, to send him pictures and a schematic drawing of your power supply. He's going to need to make one.
10/27/2009 3:16:41 PMGeorge....OHHH WOW
Yah ..but this power supply is way way to complex...It was built even better than the Arbe power supply...Who-ever built this ..was a electronics whizz ..way beyond me...

:George. It would be cool of you, to send him pictures and a schematic drawing of your power supply. He's going to need to make one.
:

10/28/2009 7:53:12 PMEdd








Sir Mike Beeeeeee . . . . .




I will contribute my part to the realizaton of the reincarnation of that unit via pulling up and clarifying your units schematic a bit,
with main emphasis on adding the interfacing to the battery supplies that the unit would have used.


The other consideraton, that it might be another 50 years before finding that specific speaker, so an interfacing to a modern
easily available PM speaker is shown in the upper corner inset that I have added.


Also check the URL that I am placing below and the possibilities of an output transformer from the list of those values that
were pulled up on my Excel spreadsheet of their inventory.


Now, if you luck out, you might find that first unit on the list at only $1.75 . . "Amellican Dollah".


Otherwise, work your way down the whole list on querying them . . . . . . any of those units should work fine.


Your call on the speaker, with just about of those output transformers secondarys being for 3.2 - 3.5 - 4 ohm

(all same same)


These output transformers below are listed at:




http://www.oldradioparts.com/2a23dfl.txt




1326-507 OUTPUT MERIT A-3026 SP (5K Z) TO 3.2 VC, 40MA, 3 WATTS, FIG 3, 2" PRI LEADS, U 1 2 3/8 1 1/4 1 0/0 $1.75


1326-508 OUTPUT MERIT A-2930 SP (5K Z) TO 3.2 VC, 40MA, 5 WATTS, FIG 3 NEW (NO BOX).... 1 2 3/8 1 3/8 1 1/4 $5.75


1329-711 OUTPUT STANCOR A-3877 SP (5K Z) TO 4 VC,, 5 WATTS, 40MA, FIG 3, NEW............. 1 2 3/8 1 3/8 1 1/4 $7.75


1330-384 OUTPUT STANCOR A-3877 SP (5K Z) TO 4 VC, 40MA, 5 WATTS, FIG 3, USED VGD......... 1 2 3/8 1 3/8 1 1/8 $4.50


1347-100 OUTPUT ADMIRAL 79D33-23 SP (5K Z) TO V.C, 45MA PRI, 5-8 WATTS, FIG 3, NEW......... 1 2 3/4 1 5/8 1 1/2 $7.75


1527-587 OUTPUT MERIT A-2930 SP (5K Z) TO 3.2 VC, 3-5 WATTS, FIG 3, USED............... 1 2 3/8 1 3/8 1 1/4 $3.75


4536-272 OUTPUT MERIT A-2930 SP (5K Z) TO 3.5 VC, 5 WATTS, 40MA, FIG 3, NEW............ 1 2 3/8 1 3/8 1 1/8 $8.50


4567-117 OUTPUT STANCOR A-3877 SP (5K Z) TO 4 OHM VC, 40MA, 5 WATTS, FIG 3, USED......... 1 2 3/8 1 3/8 1 1/4 $3.75


4575-041 OUTPUT CALRAD (JAPAN) SP (5K Z) TO 3.2 V.C., 1-3 WATTS, FIG 3, NEW.............. 1 2 0/0 1 1/8 1 0/0 $4.00


4576-054 OUTPUT JD-105118 SP (6V6, 4-5K Z) TO V.C., 5 WATT, FIG 3, USED............. 1 2 1/2 1 7/8 1 3/8 $4.25


4577-086 OUTPUT ZENITH 95-2797 SP (6Z10 TUBE, 5K Z) TO VC (4 OHMS?), 3-5W, FIG 3, USED... 1 2 3/8 1 3/8 1 1/4 $3.75


4578-022 OUTPUT MERIT A-2935 SP/PP TO 3.2 VC, PRI 5KCT Z, 18 WATTS, FIG 3, USED........ 1 3 1/4 1 7/8 1 1/2 $12.50



The logical solution for the battery power solution would be building up of a line powered power supply.


aka . . . battery eliminator.


My choice / procedure would be power line AC inputting into a power transformer rated at 120vac to 6v(or 12V ct) to another 6v(or 12V ct) to 120vac of the second same type of unit (but, notice that the second transformer is reversed to match to the voltage output of the first one.)


In that maner, the voltage for the A supply could be rectified and regulated from the center VAC supply. Also there is the need to
get an ultra super micro miniscule amount of power for the - C supply from that winding.


At the secondary winding of the second transformer, there would be present, a dupe of your AC line input voltage, which you would then rectify, filter and regulate down to 135 VDC. You then dump that into a resistive voltage divider network to permit the tap offs from it to then acquire the +90 and + 45 supply points.




Standing By . . . (hoping that your electro--proficiency far exceeds stringing and interfacing CAT-5 and coax within the nooks and crannies . . .and that's HEAVY on the crannies of Summit Telecom Risers and Chases,)





ASIDE:       
"George" . . "George" . . .are you there ?                   Can you hear me now ?


If you could provide a series of close up photos of the mentioned existant power supply of your's
components and layout.


I just might be able to see its degree of involvement / (design worthiness!) and make up a schema of it.






73's de Edd







Jah ! . . . . . icht bin der Amerikanski BOSCH 16:










10/28/2009 8:11:03 PMPulled colons- -Reindexed text








Sir Mike Beeeeeee . . . . .




I will contribute my part to the realizaton of the reincarnation of that unit via pulling up and clarifying your units schematic a bit,
with main emphasis on adding the interfacing to the battery supplies that the unit would have used.


The other consideraton, that it might be another 50 years before finding that specific speaker, so an interfacing to a modern
easily available PM speaker is shown in the upper corner inset that I have added.


Also check the URL that I am placing below and the possibilities of an output transformer from the list of those values that
were pulled up on my Excel spreadsheet of their inventory.


Now, if you luck out, you might find that first unit on the list at only $1.75 . . "Amellican Dollah".


Otherwise, work your way down the whole list on querying them . . . . . . any of those units should work fine.


Your call on the speaker, with just about of those output transformers secondarys being for 3.2 - 3.5 - 4 ohm

(all same same)


These output transformers below are listed at:




http://www.oldradioparts.com/2a23dfl.txt




1326-507 OUTPUT MERIT A-3026 SP (5K Z) TO 3.2 VC, 40MA, 3 WATTS, FIG 3, 2" PRI LEADS, U 1 2 3/8 1 1/4 1 0/0 $1.75


1326-508 OUTPUT MERIT A-2930 SP (5K Z) TO 3.2 VC, 40MA, 5 WATTS, FIG 3 NEW (NO BOX).... 1 2 3/8 1 3/8 1 1/4 $5.75


1329-711 OUTPUT STANCOR A-3877 SP (5K Z) TO 4 VC,, 5 WATTS, 40MA, FIG 3, NEW............. 1 2 3/8 1 3/8 1 1/4 $7.75


1330-384 OUTPUT STANCOR A-3877 SP (5K Z) TO 4 VC, 40MA, 5 WATTS, FIG 3, USED VGD......... 1 2 3/8 1 3/8 1 1/8 $4.50


1347-100 OUTPUT ADMIRAL 79D33-23 SP (5K Z) TO V.C, 45MA PRI, 5-8 WATTS, FIG 3, NEW......... 1 2 3/4 1 5/8 1 1/2 $7.75


1527-587 OUTPUT MERIT A-2930 SP (5K Z) TO 3.2 VC, 3-5 WATTS, FIG 3, USED............... 1 2 3/8 1 3/8 1 1/4 $3.75


4536-272 OUTPUT MERIT A-2930 SP (5K Z) TO 3.5 VC, 5 WATTS, 40MA, FIG 3, NEW............ 1 2 3/8 1 3/8 1 1/8 $8.50


4567-117 OUTPUT STANCOR A-3877 SP (5K Z) TO 4 OHM VC, 40MA, 5 WATTS, FIG 3, USED......... 1 2 3/8 1 3/8 1 1/4 $3.75


4575-041 OUTPUT CALRAD (JAPAN) SP (5K Z) TO 3.2 V.C., 1-3 WATTS, FIG 3, NEW.............. 1 2 0/0 1 1/8 1 0/0 $4.00


4576-054 OUTPUT JD-105118 SP (6V6, 4-5K Z) TO V.C., 5 WATT, FIG 3, USED............. 1 2 1/2 1 7/8 1 3/8 $4.25


4577-086 OUTPUT ZENITH 95-2797 SP (6Z10 TUBE, 5K Z) TO VC (4 OHMS?), 3-5W, FIG 3, USED... 1 2 3/8 1 3/8 1 1/4 $3.75


4578-022 OUTPUT MERIT A-2935 SP/PP TO 3.2 VC, PRI 5KCT Z, 18 WATTS, FIG 3, USED........ 1 3 1/4 1 7/8 1 1/2 $12.50



The logical solution for the battery power solution would be building up of a line powered power supply.


aka . . . battery eliminator.


My choice / procedure would be power line AC inputting into a power transformer rated at 120vac to 6v


(or 12V ct) to another 6v(or 12V ct) to 120vac of the second same type of unit (but, notice that the second


transformer is reversed to match to the voltage output of the first one.)


In that maner, the voltage for the A supply could be rectified and regulated from the center VAC supply.


Also there is the need to get an ultra super micro miniscule amount of power for the - C supply from that winding.



At the secondary winding of the second transformer, there would be present, a dupe of your AC line input voltage,


which you would then rectify, filter and regulate down to 135 VDC. You then dump that into a resistive voltage


divider network to permit the tap offs from it to then acquire the +90 and + 45 supply points.




Standing By . . . (hoping that your electro--proficiency far exceeds stringing and interfacing CAT-5 and coax within


the nooks and crannies . . .and that's HEAVY on the crannies of Summit Telecom Risers and Chases,)




ASIDE:       
"George" . . "George" . . .are you there ?                   Can you hear me now ?


If you could provide a series of close up photos of the mentioned existant power supply of your's
components and layout.


I just might be able to see its degree of involvement / (design worthiness!) and make up a schema of it.






73's de Edd







Jah ! . . . . . icht bin der Amerikanski BOSCH 16:










10/29/2009 11:29:19 AMMike B
:Yah ..but this power supply is way way to complex...It was built even better than the Arbe power supply...Who-ever built this ..was a electronics whizz ..way beyond me...
:
::George. It would be cool of you, to send him pictures and a schematic drawing of your power supply. He's going to need to make one.
::
:
10/29/2009 12:59:24 PMTerry Decker
::Yah ..but this power supply is way way to complex...It was built even better than the Arbe power supply...Who-ever built this ..was a electronics whizz ..way beyond me...
::
:::George. It would be cool of you, to send him pictures and a schematic drawing of your power supply. He's going to need to make one.
:::
::
:
:I actually ended up talking to David Snow and purchased an ARBE III. He and I have been corresponding and he is also going to include a wiring diagram so that I know how to wire the thing up.
:
:George,
:
:I was able to get some tubes from a retailer on eBay: DavidAndrews Tubes.
:
:As far as a speaker goes, I found a 1920's era Thorola in really nice condition. Now I am just waiting for all the goodies to show up so I can start this experiment....
:
:
:
10/29/2009 1:02:54 PMTerry Decker
:::Yah ..but this power supply is way way to complex...It was built even better than the Arbe power supply...Who-ever built this ..was a electronics whizz ..way beyond me...
:::
::::George. It would be cool of you, to send him pictures and a schematic drawing of your power supply. He's going to need to make one.
::::
:::
::
::I actually ended up talking to David Snow and purchased an ARBE III. He and I have been corresponding and he is also going to include a wiring diagram so that I know how to wire the thing up.
::
::George,
::
::I was able to get some tubes from a retailer on eBay: DavidAndrews Tubes.
::
::As far as a speaker goes, I found a 1920's era Thorola in really nice condition. Now I am just waiting for all the goodies to show up so I can start this experiment....
::
::
::
:
Good news- Antique Electronic supply has a power supply kit for early battery radios. Model K-101-A. It sells for just $53.95
11/9/2009 8:06:14 PMMike B
George,

I have everything hooked up and got the tubes to light up. What voltages do your yellow and yellow/black wire get??? That's the only thing I can't figure out. Thank you for the help!

11/9/2009 8:17:30 PMcarl z
:George,
:
:I have everything hooked up and got the tubes to light up. What voltages do your yellow and yellow/black wire get??? That's the only thing I can't figure out. Thank you for the help!
:
11/10/2009 2:04:44 AMEdd






Sir Mike . . . . .




Those given color codings seem to be in accordance with the model 27 Amborada INSTEAD of your model 16 Ambrola.


PLUS, I don't even think that you could rely on persistence of wire color code dyes . .except for black . .after ALL of those decades.


Best to be SURE, and pull out ye olde ohmmeter and confirm a specific terminal as going to some component as is specified on the schematic.


Unless the physical , side by side terminal lay out does seem to confirm then being in sequential order, after multiple checks of a few terminals.


Also, methinks that selection of -9 on the "C" level would be impinging well up into the tubes 1st grid cut off curves, and choppy audio at higher AF levels would probably be that higher selections choice.


The "C" is placed in series- adding WITH the "A" voltage supply, so the -4.5 of "C" level, might be more in order for its selected value.


The large schematic of the unit is below . .with mark-ups.





73's de Edd








Le Schematique:




American Bosch Model 16 The "Ambrola":








::George,
::
::I have everything hooked up and got the tubes to light up. What voltages do your yellow and yellow/black wire get??? That's the only thing I can't figure out. Thank you for the help!
::
:

11/10/2009 3:40:04 PMMike B
Edd,

Thank you. The colors are in really good shape so I am positive of their appearance.

Question: I took the radio out of the wood box and underneath on the terminal strip it looks like there are two wires missing. If I am reading the schematic correclty, this would be where the white and salmon wires go...

Also, all tubes light up except tube 1AF... Are the wires just possibly missing?

Everything appears to be working the way it should but I can't get any sound out of the speaker.

Thank you.

11/10/2009 7:46:31 PMGeorge ...Mike
I had to put a new wire harness on mine let me pull mine apart and give you the wire line-up I will describe in next posting


:George,
:
:I have everything hooked up and got the tubes to light up. What voltages do your yellow and yellow/black wire get??? That's the only thing I can't figure out. Thank you for the help!
:

11/10/2009 7:51:34 PMMike B
I just put a new harness on mine as well. The wires were really brittle. I just don't know what to do with the yellow and yellow/black wires. Everything else is hooked up now and I have sound. There doesn't seem to be any volume control though. There are three pots on the board but I don't know what each one does... Is this a fixed volume unit?

Thanks George!

11/10/2009 7:58:40 PMGeorge...Mike
Give me 30 mnts and check back here will give you info

:I just put a new harness on mine as well. The wires were really brittle. I just don't know what to do with the yellow and yellow/black wires. Everything else is hooked up now and I have sound. There doesn't seem to be any volume control though. There are three pots on the board but I don't know what each one does... Is this a fixed volume unit?
:
:Thanks George!
:

11/10/2009 8:25:41 PMGeorge......MIKE
Ok I pulled out my chassis ....If you flip chassis over and have knobs pointing away from you and from right to left...(the solder lugs) from the right... 1. is +45 2. No hook up 3. -4.5 4. A- B- 5.& 6.are hooked together and is A+ 7. 90+ 8. 135
9. -9 Hope this helps ..any more info let me know....will leave chassis upside down and out of case for a day


:Give me 30 mnts and check back here will give you info
:
::I just put a new harness on mine as well. The wires were really brittle. I just don't know what to do with the yellow and yellow/black wires. Everything else is hooked up now and I have sound. There doesn't seem to be any volume control though. There are three pots on the board but I don't know what each one does... Is this a fixed volume unit?
::
::Thanks George!
::
:

11/11/2009 11:57:31 AMMike B
George,

It is obviously beyond me... I tried hooking it up the way that David with ARBE III told me and I was able to get a local station yesterday loud and clear but really didn't have any control over the volume.

Today I tried to wire it the way you said in your email and it still works but now one of the tubes is not lighting. I switched it out with 4 other working tubes and it still doesn't light up and all I get is static.

I don't think that the wiring is the issue now. Now I think there is something wrong with the tube... Looking at the top of the unit with the knobs facing you, it would be tube #5 working from left to right.

All the other tubes light up but all I get is a hum...

I guess what I need to do now is ask the forum if there is an expert out there that would like to work on this unit for me and restore it to working order.

Being new to the forum, is there anyone out there that I could ship this to that knows the Bosch models really well?

Thank you.

11/11/2009 9:53:29 PM<b>Edd</b>







Sir Mike . . . . .



Oh behold ye of little faith . . . . .Don't you " recognize" how VERY close you are to having completed your goal ?

First of all, I was amazed that the color codings on ye ode wire were still distinguishable.


Now, with your last two errant wires colors given, that seems that the two that are needing to be going to the C-minus supply.



A . . . . . I was able to get a local station yesterday loud and clear but really didn't have any control over the volume.


B . . . . . .Today I tried to wire it the way you said in your email and it still works but now one of the tubes is not lighting.



Looks like you got the afore mentioned wires hooked up correctly !


Now see if you can take in all of this .


I made a further blow up of the schematic to accomodate definition of wire color highlighting, to differentiate between
our involved circuit paths of interest.

ALSO, I think that you might additonally be having trouble associating the tube designations on the schematic,to their physical locations on the chassis proper, so those yellow boxes at the top should now eliminate any ambiguity between tubes of the same type.


Schematic rundown:


Consulting the left of the schematic we see the antenna input to the unit, so be sure to initially use a looooong wire antenna instead of a paltry 'lebenteen" ft length of hook up wire.


After you start getting positive results, you then will be able to see the degree of scaling back of antenna length that is permissible for achieving specific results..


A good antenna / aerial suggestion is to pull out a 50- 100 ' extension cord and string w--a--y-- ---o--u--t, making interfacing connection to the male pin(s).


Notice your "M" antenna switch, that is there to make connection to different input taps to optimize to the length of antenna /aerial
wire length that you have chosen. Opt for the loudest position.


Next point of interest is the " N" power switch. note its off positon and the other options to each side.


In the sliding of the right shorter brass contact to the left position, the center two bottom contacts will be shorted across, with the A+ and B- connection going up to the [SOLID GREEN ] filament buss.


Now trace it to its far right and then notice that in coming back , that it sequentially goes upwards to feed one filament wire of each tube starting with the 2AF, 1AF, DET, and then stops at the 2RF.


NOTE that the 1 RF receives no filament power when you are in this mode, as the receiver is operating with no 1st RF amp stage and is dependent upon interelectrode capacitance between the elements of that 1 RF amp to establish the signal coupling between the 1st and 2nd RF stages.


NOW can you associate that with you NOT having one tube filament lighting up ?


Now, if you need more gain from the set in the RF front end, you slide the "M" switch to its position where the other contact is bridging all three contacts and the [BLACK--GREEN] buss then starts receiving filament voltage to feed up to the 1 RF amps filament.



I didn't have any control over the volume.



Now, to look at that aspect of the problem, there are two potentials for the control of the volume, one is in the governance of the emission on the 2nd AF tube.


I purposefuly left the perspective of the A minus of the filament buss until now, as you will see, it also routed between the OTHER filament connections of each of ALL of the tube complement, with the exception of the final 3 AF tube where you will see a filament voltage control [ C ] in series, before it reaches the tubes filament connecton.


Within the limitation of the range of that control, it should be able to increase that pots in line resistance setting and decrease the filament voltage reaching its tube, and in turn, decrease its emisson with an acccompanying decrease of the gain in that stage.


DON'T expect INSTANT gratification on that adjustment, as there is a thermal delay time lag in the tube acclimating to that change in filament supply voltage.(Either up or down)


Nowwwww, back to the other aspect of volume control, utilizing less RF voltage being presented to the detector stage, via the overall gain of the 2 frontal RF amplifiers.


Now, direct your attention to the AA, B and BB controls located down under under the RF stages. Take note of the [ RED-GREEN] zebra path mark up that is highlighting a connection from the A-Fil Buss down to resistor J and then to the paralleled set of pots, A and B and the final completion of the loop to the A+ Fil Buss.


The trio make up a voltage divider across the A filament supply voltage , with the J element establisting the highest voltage attainable, along with also providing a resistive" stop " for the possible control positions of A--B--BB being set to closely to the
A-fil supply source and loading down the supply OR putting a burn . .Pf f f f f f f f t t . . on a control element, run too close to
its range end.


Then you have the BB control which is located between the A and B controls rotors. BB would be a vernier adjustment of the voltage that is acquired from that voltage divider combo and is then being fed off from its rotor, up to the 1st grids of the 1 RF and 2 RF amps to control their gains.


Now you would have to fill me in on the A-B controls ( mechanically Ganged together---or ---separate ?) as I am totally blind and no photo of the front of an AM-- BO 16 seems to be available.


Perchance are A and B ganged together, if not, the interjuxtopositioning of the three controls could give some fierce output control capabilities. BUT, in consulting the chart below, expect the range to be within the 2-4 V.


Note that at the 1st 2 RF amps, their input coils, companion tuning condenser sections are connected at their lower sides to ground and otherwise that circitry is totally apart from the rest of the sets circitry . . .DC wise, with an AC coupling interconnect aspect being made at that " F " capacitor.BUT, the DC connection to the actual chassis circuitry is made at the BB rotor , to acquire those 1st grid's control voltages.


If that condition is breached, that would be a possibility for no frontal RF Gain comtrol. If suspicioned, jab a negative DC metering probe into the A+ Filament Buss and the other probe to a 1st gid of an RF amp tube, then you run the pots thru the variants to see if the 2-4 V adjustment range is being present at the 1st grids of the RF amp tubes.




Awaiting feed back . . . if necessary . . . plus an answer on the pots info query.







73's de Edd






American BOSCH 16 Schematic Markup:















:George,
:
:It is obviously beyond me... I tried hooking it up the way that David with ARBE III told me and I was able to get a local station yesterday loud and clear but really didn't have any control over the volume.
:
:Today I tried to wire it the way you said in your email and it still works but now one of the tubes is not lighting. I switched it out with 4 other working tubes and it still doesn't light up and all I get is static.
:
:I don't think that the wiring is the issue now. Now I think there is something wrong with the tube... Looking at the top of the unit with the knobs facing you, it would be tube #5 working from left to right.
:
:All the other tubes light up but all I get is a hum...
:
:I guess what I need to do now is ask the forum if there is an expert out there that would like to work on this unit for me and restore it to working order.
:
:Being new to the forum, is there anyone out there that I could ship this to that knows the Bosch models really well?
:
:Thank you.
:

11/11/2009 11:40:55 PMEdd. . . .RESET right Indexing







Sir Bill. . . . .


Oh behold ye of little faith . . . . .Don't you " recognize" how VERY close you are to having completed your goal ?

Initially, I was amazed that the color codings on ye ode wire were still distinguishable.

Now, with your last two errant wires colors given, that seems that the two that are needing to be going to the C-minus supply.

A . . . . . I was able to get a local station yesterday loud and clear but really didn't have any control over the volume.


B . . . . . .Today I tried to wire it the way you said in your email and it still works but now one of the tubes is not lighting.


Looks like you got the afore mentioned wires hooked up correctly !

Now lets see the degree of applicability of this info to your situaton.

I made a further blow up of the schematic to accomodate definition of wire color highlighting, to differentiate between
our involved circuit paths of interest.

ALSO, I think that you might additonally be having trouble associating the tube designations on the schematic,to their physical locations on the chassis proper, so those yellow boxes at the top should now eliminate any ambiguity between tubes of the same type.


Schematic rundown:


Consulting the left of the schematic we see the antenna input to the unit, so be sure to initially use a looooong wire antenna instead of a paltry 'lebenteen" ft length of hook up wire. After you start getting positive results, you then will be able to see the degree of scaling back of antenna length that is permissible for achieving specific results..

A good antenna / aerial suggestion is to pull out a 50- 100 ' extension cord and string w--a--y-- ---o--u--t, making interfacing connection to the male pin(s).


Notice your "M" antenna switch, that is there to make connection to different input taps to optimize to the length of antenna /aerial wire length that you have chosen. Opt for the loudest position.


Next point of interest is the " N" power switch. note its off positon and the other options to each side. In the sliding of the right shorter brass contact to the left position, the center two bottom contacts will be shorted across, with the A+ and B- connection going up to the [SOLID GREEN ] filament buss.

Now trace it to its far right and then notice that in coming back , that it sequentially goes upwards to feed one filament wire of each tube starting with the 2AF, 1AF, DET, and then stops at the 2RF.


NOTE that the 1 RF receives no filament power when you are in this mode, as the receiver is operating with no 1st RF amp stage and is dependent upon interelectrode capacitance between the elements of that 1 RF amp to establish the signal coupling between the 1st and 2nd RF stages.


NOW can you associate that with you NOT having one tube filament lighting up ?


Now, if you need more gain from the set in the RF front end, you slide the "M" switch to its position where the other contact is bridging all three contacts and the [BLACK--GREEN] buss then starts receiving filament voltage to feed up to the 1 RF amps filament.



I didn't have any control over the volume.



Now, to look at that aspect of the problem, there are two potentials for the control of the volume, one is in the governance of the emission on the 2nd AF tube.

I purposefuly left the perspective of the A minus of the filament buss until now, as you will see, it also routed between the OTHER filament connections of each of ALL of the tube complement, with the exception of the final 3 AF tube where you will see a filament voltage control [ C ] in series, before it reaches the tubes filament connecton.


Within the limitation of the range of that control, it should be able to increase that pots in line resistance setting and decrease the filament voltage reaching its tube, and in turn, decrease its emisson with an acccompanying decrease of the gain in that stage.
DON'T expect INSTANT gratification on that adjustment, as there is a thermal delay time lag in the tube acclimating to that change in filament supply voltage.(Either up or down)

Nowwwww, back to the other aspect of volume control, utilizing less RF voltage being presented to the detector stage, via the overall gain of the 2 frontal RF amplifiers.

Now, direct your attention to the AA, B and BB controls located down under under the RF stages. Take note of the [RED-GREEN] zebra path mark up that is highlighting a connection from the A-Fil Buss down to resistor J and then to the parallel set of pots, A and B and the final completion of the loop to the A+ Fil Buss.
The trio make up a voltage divider across the A filament supply voltage , with the J resistor element establisting the highest voltage attainable, along with also providing a resistive" stop " for the possible control positions of A--B--BB being set to closely to the A-fil supply source and loading down the supply OR putting a burn . .Pf f f f f f f f t t . . on a control element, run too close to its range end.

Then you have the BB control which is located between the A and B controls rotors. BB would be a vernier adjustment of the voltage that is acquired from that voltage divider combo and is then being fed off from its rotor, up to the 1st grids of the 1 RF and 2 RF amps to control their gains.


Now you would have to fill me in on the A-B controls ( mechanically Ganged together---or ---separate ?) as I am totally blind and no photo of the front of an AM-- BO 16 seems to be available.

Perchance are A and B ganged together, if not, the interjuxtopositioning of the three controls could give some fierce output control capabilities. BUT, in consulting the chart below, expect the range to be within the 2-4 V range.


Note that at the 1st 2 RF amps, their input coils, companion tuning condenser sections are connected at their lower sides to ground, and otherwise, that circitry is totally apart from the rest of the sets circitry . . .DC wise, with their AC coupling interconnect aspect being made with that " F " capacitor.BUT, the DC connection to the actual chassis circuitry is solely made at the BB pots rotor , to acquire those 1st grid's control voltages.


If that condition is breached, that would be a possibility for no frontal RF Gain comtrol. If so suspicioned, jab a negative DC metering probe into the A+ Filament Buss and the other probe to a 1st grid of an RF amp tube, then you run the pots thru the variants to see if the 2-4 V adjustment range is being present at the 1st grids of the RF amp tubes.

Awaiting feed back . . . if necessary . . . plus an answer on the pots info query.


73's de Edd






American BOSCH 16 Schematic Markup:









:
:



:
:
:
::George,
::
::It is obviously beyond me... I tried hooking it up the way that David with ARBE III told me and I was able to get a local station yesterday loud and clear but really didn't have any control over the volume.
::
::Today I tried to wire it the way you said in your email and it still works but now one of the tubes is not lighting. I switched it out with 4 other working tubes and it still doesn't light up and all I get is static.
::
::I don't think that the wiring is the issue now. Now I think there is something wrong with the tube... Looking at the top of the unit with the knobs facing you, it would be tube #5 working from left to right.
::
::All the other tubes light up but all I get is a hum...
::
::I guess what I need to do now is ask the forum if there is an expert out there that would like to work on this unit for me and restore it to working order.
::
::Being new to the forum, is there anyone out there that I could ship this to that knows the Bosch models really well?
::
::Thank you.
::
:

11/12/2009 3:11:34 PMEdd . .3rd time. .the charm ?






Sir Mike Beeee. . . . .


Oh behold ye of little faith . . . . .Don't you " recognize" how VERY close you are to having completed your goal ?

Initially, I was amazed that the color codings on ye ode wire were still distinguishable.

Now, with your last two errant wires colors given, that seems that the two that are needing to be going to the C-minus supply.

A . . . . . I was able to get a local station yesterday loud and clear but really didn't have any control over the volume.


B . . . . . .Today I tried to wire it the way you said in your email and it still works but now one of the tubes is not lighting.


Looks like you got the afore mentioned wires hooked up correctly !

Now lets see the degree of applicability of this info to your situaton.

I made a further blow up of the schematic to accomodate definition of wire color highlighting, to differentiate between
our involved circuit paths of interest.

ALSO, I think that you might additonally be having trouble associating the tube designations on the schematic,to their physical locations on the chassis proper, so those yellow boxes at the top should now eliminate any ambiguity between tubes of the same type.


Schematic rundown:


Consulting the left of the schematic we see the antenna input to the unit, so be sure to initially use a looooong wire antenna instead of a paltry 'lebenteen" ft length of hook up wire. After you start getting positive results, you then will be able to see the degree of scaling back of antenna length that is permissible for achieving specific results..

A good antenna / aerial suggestion is to pull out a 50- 100 ' extension cord and string w--a--y-- ---o--u--t, making interfacing connection to the male pin(s).


Notice your "M" antenna switch, that is there to make connection to different input taps to optimize to the length of antenna /aerial wire length that you have chosen. Opt for the loudest position.


Next point of interest is the " N" power switch. note its off positon and the other options to each side. In the sliding of the right shorter brass contact to the left position, the center two bottom contacts will be shorted across, with the A+ and B- connection going up to the [SOLID GREEN ] filament buss.

Now trace it to its far right and then notice that in coming back , that it sequentially goes upwards to feed one filament wire of each tube starting with the 2AF, 1AF, DET, and then stops at the 2RF.


NOTE that the 1 RF receives no filament power when you are in this mode, as the receiver is operating with no 1st RF amp stage and is dependent upon interelectrode capacitance between the elements of that 1 RF amp to establish the signal coupling between the 1st and 2nd RF stages.


NOW can you associate that with you NOT having one tube filament lighting up ?


Now, if you need more gain from the set in the RF front end, you slide the "M" switch to its position where the other contact is bridging all three contacts and the [BLACK--GREEN] buss then starts receiving filament voltage to feed up to the 1 RF amps filament.



I didn't have any control over the volume.



Now, to look at that aspect of the problem, there are two potentials for the control of the volume, one is in the governance of the emission on the 2nd AF tube.

I purposefuly left the perspective of the A minus of the filament buss until now, as you will see, it also routed between the OTHER filament connections of each of ALL of the tube complement, with the exception of the final 3 AF tube where you will see a filament voltage control [ C ] in series, before it reaches the tubes filament connecton.


Within the limitation of the range of that control, it should be able to increase that pots in line resistance setting and decrease the filament voltage reaching its tube, and in turn, decrease its emisson with an acccompanying decrease of the gain in that stage.
DON'T expect INSTANT gratification on that adjustment, as there is a thermal delay time lag in the tube acclimating to that change in filament supply voltage.(Either up or down)

Nowwwww, back to the other aspect of volume control, utilizing less RF voltage being presented to the detector stage, via the overall gain of the 2 frontal RF amplifiers.

Now, direct your attention to the AA, B and BB controls located down under under the RF stages. Take note of the [RED-GREEN] zebra path mark up that is highlighting a connection from the A-Fil Buss down to resistor J and then to the parallel set of pots, A and B and the final completion of the loop to the A+ Fil Buss.
The trio make up a voltage divider across the A filament supply voltage , with the J resistor element establisting the highest voltage attainable, along with also providing a resistive" stop " for the possible control positions of A--B--BB being set to closely to the A-fil supply source and loading down the supply OR putting a burn . .Pf f f f f f f f t t . . on a control element, run too close to its range end.

Then you have the BB control which is located between the A and B controls rotors. BB would be a vernier adjustment of the voltage that is acquired from that voltage divider combo and is then being fed off from its rotor, up to the 1st grids of the 1 RF and 2 RF amps to control their gains.


Now you would have to fill me in on the A-B controls ( mechanically Ganged together---or ---separate ?) as I am totally blind and no photo of the front of an AM-- BO 16 seems to be available.

Perchance are A and B ganged together, if not, the interjuxtopositioning of the three controls could give some fierce output control capabilities. BUT, in consulting the chart below, expect the range to be within the 2-4 V range.


Note that at the 1st 2 RF amps, their input coils, companion tuning condenser sections are connected at their lower sides to ground, and otherwise, that circitry is totally apart from the rest of the sets circitry . . .DC wise, with their AC coupling interconnect aspect being made with that " F " capacitor.BUT, the DC connection to the actual chassis circuitry is solely made at the BB pots rotor , to acquire those 1st grid's control voltages.


If that condition is breached, that would be a possibility for no frontal RF Gain comtrol. If so suspicioned, jab a negative DC metering probe into the A+ Filament Buss and the other probe to a 1st grid of an RF amp tube, then you run the pots thru the variants to see if the 2-4 V adjustment range is being present at the 1st grids of the RF amp tubes.

Awaiting feed back . . . if necessary . . . plus an answer on the pots info query.


73's de Edd






American BOSCH 16 Schematic Marked - Waaay-Up:















IPAddress: ***.225.161.130

11/12/2009 3:20:49 PM3 1/2






Sir Mike Beeee. . . . .


Oh behold ye of little faith . . . . .Don't you " recognize" how VERY close you are to having completed your goal ?

Initially, I was amazed that the color codings on ye ode wire were still distinguishable.

Now, with your last two errant wires colors given, that seems that the two that are needing to be going to the C-minus supply.

A . . . . . I was able to get a local station yesterday loud and clear but really didn't have any control over the volume.


B . . . . . .Today I tried to wire it the way you said in your email and it still works but now one of the tubes is not lighting.


Looks like you got the afore mentioned wires hooked up correctly !

Now lets see the degree of applicability of this info to your situaton.

I made a further blow up of the schematic to accomodate definition of wire color highlighting, to differentiate between
our involved circuit paths of interest.

ALSO, I think that you might additonally be having trouble associating the tube designations on the schematic,to their physical locations on the chassis proper, so those yellow boxes at the top should now eliminate any ambiguity between tubes of the same type.


Schematic rundown:


Consulting the left of the schematic we see the antenna input to the unit, so be sure to initially use a looooong wire antenna instead of a paltry 'lebenteen" ft length of hook up wire. After you start getting positive results, you then will be able to see the degree of scaling back of antenna length that is permissible for achieving specific results..

A good antenna / aerial suggestion is to pull out a 50- 100 ' extension cord and string w--a--y-- ---o--u--t, making interfacing connection to the male pin(s).


Notice your "M" antenna switch, that is there to make connection to different input taps to optimize to the length of antenna /aerial wire length that you have chosen. Opt for the loudest position.


Next point of interest is the " N" power switch. note its off positon and the other options to each side. In the sliding of the right shorter brass contact to the left position, the center two bottom contacts will be shorted across, with the A+ and B- connection going up to the [SOLID GREEN ] filament buss.

Now trace it to its far right and then notice that in coming back , that it sequentially goes upwards to feed one filament wire of each tube starting with the 2AF, 1AF, DET, and then stops at the 2RF.


NOTE that the 1 RF receives no filament power when you are in this mode, as the receiver is operating with no 1st RF amp stage and is dependent upon interelectrode capacitance between the elements of that 1 RF amp to establish the signal coupling between the 1st and 2nd RF stages.


NOW can you associate that with you NOT having one tube filament lighting up ?


Now, if you need more gain from the set in the RF front end, you slide the "M" switch to its position where the other contact is bridging all three contacts and the [BLACK--GREEN] buss then starts receiving filament voltage to feed up to the 1 RF amps filament.



I didn't have any control over the volume.



Now, to look at that aspect of the problem, there are two potentials for the control of the volume, one is in the governance of the emission on the 2nd AF tube.

I purposefuly left the perspective of the A minus of the filament buss until now, as you will see, it also routed between the OTHER filament connections of each of ALL of the tube complement, with the exception of the final 3 AF tube where you will see a filament voltage control [ C ] in series, before it reaches the tubes filament connecton.


Within the limitation of the range of that control, it should be able to increase that pots in line resistance setting and decrease the filament voltage reaching its tube, and in turn, decrease its emisson with an acccompanying decrease of the gain in that stage.
DON'T expect INSTANT gratification on that adjustment, as there is a thermal delay time lag in the tube acclimating to that change in filament supply voltage.(Either up or down)

Nowwwww, back to the other aspect of volume control, utilizing less RF voltage being presented to the detector stage, via the overall gain of the 2 frontal RF amplifiers.

Now, direct your attention to the AA, B and BB controls located down under under the RF stages. Take note of the [RED-GREEN] zebra path mark up that is highlighting a connection from the A-Fil Buss down to resistor J and then to the parallel set of pots, A and B and the final completion of the loop to the A+ Fil Buss.
The trio make up a voltage divider across the A filament supply voltage , with the J resistor element establisting the highest voltage attainable, along with also providing a resistive" stop " for the possible control positions of A--B--BB being set to closely to the A-fil supply source and loading down the supply OR putting a burn . .Pf f f f f f f f t t . . on a control element, run too close to its range end.

Then you have the BB control which is located between the A and B controls rotors. BB would be a vernier adjustment of the voltage that is acquired from that voltage divider combo and is then being fed off from its rotor, up to the 1st grids of the 1 RF and 2 RF amps to control their gains.


Now you would have to fill me in on the A-B controls ( mechanically Ganged together---or ---separate ?) as I am totally blind and no photo of the front of an AM-- BO 16 seems to be available.

Perchance are A and B ganged together, if not, the interjuxtopositioning of the three controls could give some fierce output control capabilities. BUT, in consulting the chart below, expect the range to be within the 2-4 V range.


Note that at the 1st 2 RF amps, their input coils, companion tuning condenser sections are connected at their lower sides to ground, and otherwise, that circitry is totally apart from the rest of the sets circitry . . .DC wise, with their AC coupling interconnect aspect being made with that " F " capacitor.BUT, the DC connection to the actual chassis circuitry is solely made at the BB pots rotor , to acquire those 1st grid's control voltages.


If that condition is breached, that would be a possibility for no frontal RF Gain comtrol. If so suspicioned, jab a negative DC metering probe into the A+ Filament Buss and the other probe to a 1st grid of an RF amp tube, then you run the pots thru the variants to see if the 2-4 V adjustment range is being present at the 1st grids of the RF amp tubes.

Awaiting feed back . . . if necessary . . . plus an answer on the pots info query.


73's de Edd






American BOSCH 16 Schematic Marked - Waaay-Up:










11/12/2009 6:49:19 PMMike B
George,

Thank you so much for pulling down the radio...

Here are the actual wiring connections on my Bosch, working in the same orientation as you (knobs away, right to left).

Pin 1: Blue
Pin 2: Yellow/Black
Pin 3: Red
Pin 4: Jumpered to Pin 3
Pin 5: Jumpered to Pin 6
Pin 6: Black
Pin 7: Brown
Pin 8: Green
Pin 9: Yellow

Dave Snow with ARBE III told me to hook it up as follows:

Pin 1: Blue (+45)
Pin 2: Yellow/Black (Don't Know)
Pin 3: Red (A+)
Pin 4: No Wire (Don't Know)
Pin 5: No Wire (Don't Know)
Pin 6: Black (A-)
Pin 7: Brown (+90)
Pin 8: Green (+135)
Pin 9: Yellow (Don't Know)

Additionally he said to jumper Red (A+) to (B-) and jumper (A-) to (C+) on the ARBEIII.

Do you have a Salmon or White wire on your chasis?

11/13/2009 2:17:49 AMGeorge.....Mike
When i got my #16 it had a VERY neat power supply tucked underneath chassis....The original battery supply wires were removed....before I removed the batter supply and I noted how it was hooked up and made a new "cable" of wires to hook up to my Arbe III.... Here is what I have for connections from right to left (Mine works!!) 1. +45 2.I have nothing hooked up to this connection 3. -4C 4. A- B+ 5.&6. A+ 7. 90+ 8. 135 9. -9C Also I put radio back together already...so not sure if there should be a jumper between 4 & 3 my guess is ther should not be because # 3 was the -4c supply and that was usually a separate small battery

:George,
:
:Thank you so much for pulling down the radio...
:
:Here are the actual wiring connections on my Bosch, working in the same orientation as you (knobs away, right to left).
:
:Pin 1: Blue
:Pin 2: Yellow/Black
:Pin 3: Red
:Pin 4: Jumpered to Pin 3
:Pin 5: Jumpered to Pin 6
:Pin 6: Black
:Pin 7: Brown
:Pin 8: Green
:Pin 9: Yellow
:
:Dave Snow with ARBE III told me to hook it up as follows:
:
:Pin 1: Blue (+45)
:Pin 2: Yellow/Black (Don't Know)
:Pin 3: Red (A+)
:Pin 4: No Wire (Don't Know)
:Pin 5: No Wire (Don't Know)
:Pin 6: Black (A-)
:Pin 7: Brown (+90)
:Pin 8: Green (+135)
:Pin 9: Yellow (Don't Know)
:
:Additionally he said to jumper Red (A+) to (B-) and jumper (A-) to (C+) on the ARBEIII.
:
:Do you have a Salmon or White wire on your chasis?
:

11/13/2009 4:51:53 AMEdd






Sir Mike B . . . . .



I think that I see your concern, you are still uncertain of the wire connections between the Arby Burger III and the set.
When I blew up the schema, the connections were left the same as the schematic was showing.


I have taken what info you included in your last " Posted by Mike B on DTG 11/12/2009 18:49 " on the connections given and
retrieved some info that I only vaguely remembered the source of, but it turned out to be from that sole post of yours back
there that got no response, since all activity was being continued here.


I now have accounted for all of your wires routing that you mentioned IF you still have an errant salmon and a white wire
left, that you did not list just below, by virtue of your solely inserting in " jumpered to ", with no further details.


Your are saying that your units wire colors are :




Pin 1: Blue


Pin 2: Yellow/Black


Pin 3: Red


Pin 4: Jumpered to Pin 3


Pin 5: Jumpered to Pin 6


Pin 6: Black


Pin 7: Brown


Pin 8: Green


Pin 9: Yellow




Dave Snows supplemental info, and the voltage connections that are made to the Arby Burger:


Pin 1: Blue (+45) . . . . . .Correct


Pin 2: Yellow/Black (Don't Know) . . . . . [It is your C+voltage connection and is jumpered on your set to the A- supply]


Pin 3: Red (A+) . . . . . . Correct


Pin 4: No Wire (Don't Know) . . . . . [ It is your B- voltage connection and is jumpered on your set to the A+ supply ]


Pin 5: No Wire (Don't Know) . . . . . [ Hopefully this term is your WHITE wire and needs to go to the -4.5 V of the Arby Burger ]


Pin 6: Black (A-) . . . . . Correct


Pin 7: Brown (+90) . . . Correct


Pin 8: Green (+135) . . .Correct


Pin 9: Yellow (Don't Know) . . . . . [ Hopefully this term is your SALMON wire and needs to go to the -9 V of the Arby Burger ]

Then he said:


Additionally he said to jumper Red (A+) to (B-) and jumper (A-) to (C+) on the ARBEIII.


That is correct . . .even though one of those connections would have been done with the jumpers within the Am Bosch set.


See if this very bottom info to this post doesn't get your set percolating and then also refer to the" post-post-post-po " . .
info , I earlier posted for info on volume control and other aspects of the set also being explained.


Also the non lighting tube, and one other thing I now thought of was the filament on the AF output tube ,


If that is the nonlighting tube instead of the 1st RF, that filament control pot just might be able to decrease the supply
enough for it to seem as if the tube is not lighting, Considering that you are expecting, but not seeing a fully red filament.
Confirm if this info presented below, will finally get the set percolating . . . .









73's de Edd





11/13/2009 1:10:40 PMMike B
Ed,

I am incredibly thankful for all your help!

I wired up the unit the way you said to and I did some testing on the one tube that was not lighing up. The tube was good. The resistor was bad. I went down to the local electronics store and got a 1.8 Ohm, 2W resistor and inserted it where the old one was. The radio works great!!!!!!

I am able to control the volume of the unit by using the Antenna knob, going from 0 to 3 increases the volume.

I also wanted to clarify the wiring connections that I initially gave you and double check with you that I have done it correctly.

There are a series of 9 solder terminals on the radio chassis where the wires are connected. With the set upside down and the knobs facing away from me and working from left to right, the wire colors on the corresponding pins are as follows:

Pin 1: Yellow
Pin 2: Green
Pin 3: Brown
Pin 4: Black
Pin 5: No Wire But is jumpered to Pin 4 on the radio.
Pin 6: No Wire But is jumpered to Pin 7 on the radio.
Pin 7: Red
Pin 8: Yellow/Black
Pin 9: Blue

My current hook up to the ARBE III is as follows:

Pin 1: Yellow: -9
Pin 2: Green: 135
Pin 3: Brown: 90
Pin 4: Black: A-
Pin 5: No Physical Connection to ARBE III but is connected to Pin 4: (Black) inside the radio.
Pin 6: No Physical Connection to ARBE III but is connected to Pin 7: (Red) inside the radio.
Pin 7: Red: A+
Pin 8: Yellow/Black: C+ jumpered to A- on the ARBE III.
Pin 9: Blue: 45.

Thanks again Ed!

11/13/2009 5:33:53 PMMike B
Ed,

One more question Sir... I am finding now that after replacing two of the older resistors with new ones, the radio seems to be working better and better. Do you think I should I replace all of them? I feel on one hand that it ruins the antique aspect of the radio if I do, but like I said, after having done two, the quality of the reception has gotten substantially better...

Thank you for your advice.



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