Keeps playing loud

8/8/2013 3:42:48 PMBob

Rider 13-79 Mont-ward Model 93wg668, replaced with new volume control (500,000 ohm) when turned down radio is loud, only get louder when turned up,old volume control did the the same thats why I replaced it.Guess that was not the problem,any ideas??

8/8/2013 5:20:13 PMCV

Bad ground connection at end of pot opposite that from the input. Bad solder joint, broken wire inside insulation...?

8/8/2013 9:42:53 PMBob

Rechecked wires & did not find anything wrong,played ok then this loud playing started not sure whats the next step.

8/8/2013 10:40:11 PMCV

Can't possibly be anything other than loss of ground at one end of pot. If ground is OK at the pot terminal, maybe the track cracked internally. Can ohm
center contact to the ground side; if it doesn't show zero ohms at one end of travel, pot is bad.
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8/9/2013 11:57:45 AMEdd

Sir Bob . . . . .

I'll tell you whut I "thunks".

First of all , if you wuz even alives back at that sets debut date in 1941-42 . . . . (Alive in Forty Five ! . . . would have rhymed ). . . . . . you would have been cognizant of the sizeable chunk of change, in those days income, that a set of batteries would have set you back.

Also, in the Dubble-ya Dubble-ya II war years of 41---45 . . . . IF you could even GET a set-of batteries, due to the war efforts availibility of items and rationing.

Now after spot checking the sets design, via schematic, I can see their opting to have the sets volume not being capable of a TOTAL silencing.

That prevention, being in case one had turned the volume down to be able to speak over it, temporarily, to another nearby person, and then TOTALLY forgetting about it.

Since, had the set TOTALLY quenched the volume, that's creating the situation of then forgetting that the radio was even being turned on, and a total drain on the battery pack . . . .mainly the "A" batteries . . . since B drain diminishes as the filament temps taper down with "A" battery depletion.
Hours, or even days later.

( If I say something TWICE, or even THRICE, there is a better chance of it being remembered ONCE. )

(As instructional cadre at West Point. )

Testee-testee # 1 . . . . .

Get out a set of test jumper wires with clips and we will confirm some "thangs".

Radio playing, volume control at MINIMUM, ground one wires clip and take its other clip to the top grid cap of the 1H5 toobie for a few seconds . . . . complete silence . . .right ?

Testee-testee # 2 . . . . .

Set is unplugged:

Then get out an electrolytic capacitor of 100 ufd and of a 3VDC UPWARDS rating and short is leads together initially.

Then it gets clipped into circuit with its negative led clipped to chassis ground and the second clip lead connecting its positive lead to the common juncture of filament and capacitor connections:

Pin 2 of the 1H5----pin 7 of the 1A7 and the ungrounded lead of the C4 bypass / decoup-li-tating capaci-tate-or.

Plug in ye olde ray-de-on and you should then find it then being :" quiet city " at minimum position of the vol-you-me control .

Explanation:

As the set was initially configured. it was impossible for the "low" side of the volume control being COMPLETELY returned to ground due to the series inserted resistance of the 1H5 filament resistance . . . . . BEING in the order of a WARMED UP / hot resistance of ~ 25 ohms.

Since you will probably " nevah-evah " have batteries installed, and be using it in AC operative mode only, install that cap, only in the case that you want full muted volume control action.

Thassssit

73's de Edd

If a tree falls in the forest and nobody is around . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . the firewood is yours for the taking . . . . (Fooled 'ya).
.

:Can't possibly be anything other than loss of ground at one end of pot. If ground is OK at the pot terminal, maybe the track cracked internally. Can ohm
:center contact to the ground side; if it doesn't show zero ohms at one end of travel, pot is bad.
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8/9/2013 4:55:44 PMBob

Ed;test # 1, placed one end of jumper cable to chassis (ground) other to top of 1H5 toobie for a few seconds and then more with no
decrease in volume, another problem? I wasn't alive in 45-try 46 pretty old you think??

8/9/2013 5:10:28 PMBob

Ed; I removed wire from top of 1H5 radio still played,looked original as if no other work from past, guess I'll look again at schematic might find something I missed. Any thoughts.

8/10/2013 8:18:50 PMLewis

:Ed; I removed wire from top of 1H5 radio still played,looked original as if no other work from past, guess I'll look again at schematic might find something I missed. Any thoughts.
:

Bob:
I think Edd is exacterlay right, the radio is designed not to be turned all the way down, to keep form running the batteries down. If all the way down is not quiet enuff, turn it off.
Lewis

8/11/2013 9:47:29 PMBob

Lewis; I also agree with Edd about volume not being able to be turned all the way down so people won't drain batteries. This is a nice radio that played good but for unknown reasons the volume increased to very loud almost full volume with turned all the way down,I replaced volume control with a new one checked wires & other parts
with the same results. NOT being blessed with the great knowledge of some people about radios & willing to share their advise to help others

, your answer to "turn off the radio" is not what "Nostalgia Air" is all about. If all the answers where turn it off or discard radio this would not be a very good sight, don't you agree?!,but I've learned a lot. Anybody out there having any input about the volume, I'm still looking.

8/11/2013 10:23:03 PMCV

Not wanting to belabor the point; but the only reason that volume is stuck on "high" is because you have lost the ground reference on the volume control. The two ends of the pot provide audio AC in and ground, respectively, and the pot wiper (center contact) is able to pick off a "continuum" of voltages.

Ohm the wire that goes from pin 2 of the 1H5 tube to the pot; it must be zero ohms. If that checks out OK, the other possibility is that capacitor C22 has opened up. C22 provides a "virtual ground" AC-wise for the volume control pot and if that cap has gone open, you will have nearly full volume all the time regardless of the pot setting.

8/13/2013 4:04:18 PMBob

:Not wanting to belabor the point; but the only reason that volume is stuck on "high" is because you have lost the ground reference on the volume control. The two ends of the pot provide audio AC in and ground, respectively, and the pot wiper (center contact) is able to pick off a "continuum" of voltages.
:
:Ohm the wire that goes from pin 2 of the 1H5 tube to the pot; it must be zero ohms. If that checks out OK, the other possibility is that capacitor C22 has opened up. C22 provides a "virtual ground" AC-wise for the volume control pot and if that cap has gone open, you will have nearly full volume all the time regardless of the pot setting.
:
CV: I Grounded one wire from ohm meter to chassis other wire to pin 2 of 1H5 meter reads 10 ohms.

8/12/2013 5:47:36 PMLewis

:Lewis; I also agree with Edd about volume not being able to be turned all the way down so people won't drain batteries. This is a nice radio that played good but for unknown reasons the volume increased to very loud almost full volume with turned all the way down,I replaced volume control with a new one checked wires & other parts
: with the same results. NOT being blessed with the great knowledge of some people about radios & willing to share their advise to help others

Hey, Bob:
I was trying to explain the mind of the radio designer, to explain why the pot is not grounded like on most radios, not tell you how to use your radio.
Lewis

:
:
:, your answer to "turn off the radio" is not what "Nostalgia Air" is all about. If all the answers where turn it off or discard radio this would not be a very good sight, don't you agree?!,but I've learned a lot. Anybody out there having any input about the volume, I'm still looking.
:
:

8/13/2013 1:22:43 AM*** Edd ***

Sir Bob

Parte Deux . . . .

I gave you two test analysis to perform, but was even unsure of your first test with the reply being so short.

BUT if you shorted the 1st grid /cap of the 1H6 to ground, the then playing radio should have ceased its audio for that shorted out duration.

That is then confirming that there is no erroneous looping through of any audio AROUND that stage and sneaking into the final audio stage.

The real answer is then to be provided by your doing the AC shunting of the audio to ground with the 100 ufd electrolytic caps insertion that I specified.

FYI . . . . or to be even more encompassing . . . . . FEBI:

That C22 capacitor located at the 1H5---1A7 filament juncture is for RF decoupling and stage isolation.

Technically its .04 ufd of capacitance can only represent but a minimal coupling thru of any degree of an audio /AC ground path for the low side of the volume control.

With it exhibiting a quite high capacitive reactance / impedance path of:

At the low audio range of 100 cycles its exhibiting a whopping ~39,000 ohms to an AC signal component

At the mid music/speech audio range of 250-1000 cycles its exhibiting an intermediate ~4,000 ohms to an AC signal component

At the high AM radios audio range of 5000 cycles its exhibiting its lowest ~800 ohms to an AC signal component

So within all of the radios audio spectrum, the least that we would receive is but a minimal hi end tone shunting effect.

BUT it does one bang up job of RF supression, only to be bettered by the use of the lower ESR that would be provided
by a disc ceramic type of unit.

So o o o o o o o . . . . . . . further provide us with your second specified tests result . . . .

After that test, if not conclusive, I am about ready to suspect a miswire of the volume controls 3 terminals, unless you found
pristine solder joints, along with an original OEM stock control.

73's de Edd

At no time is freedom of speech more precious than when you hit your thumb with a hammer.

::Lewis; I also agree with Edd about volume not being able to be turned all the way down so people won't drain batteries. This is a nice radio that played good but for unknown reasons the volume increased to very loud almost full volume with turned all the way down,I replaced volume control with a new one checked wires & other parts
:: with the same results. NOT being blessed with the great knowledge of some people about radios & willing to share their advise to help others
:
:
:Hey, Bob:
:I was trying to explain the mind of the radio designer, to explain why the pot is not grounded like on most radios, not tell you how to use your radio.
:Lewis
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:
:
:
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::
::, your answer to "turn off the radio" is not what "Nostalgia Air" is all about. If all the answers where turn it off or discard radio this would not be a very good sight, don't you agree?!,but I've learned a lot. Anybody out there having any input about the volume, I'm still looking.
::
::
:
:

8/13/2013 6:55:30 AMCV

Edd, you need to recall that, while the C22 cap's average impedance at audio AC frequencies may be in the 10K ohm range, the resistance of the pot is 500K ohm. This relationship provides a 50:1 audio voltage divider effect when the pot wiper is set at minimum voltage output. This is not trivial.

Also note that the 1H5 tube's pin 7 ("high" side of C22) is the return point of the diode element in that tube which is used as the audio demodulator.

8/13/2013 4:08:40 PMBob

:Edd, you need to recall that, while the C22 cap's average impedance at audio AC frequencies may be in the 10K ohm range, the resistance of the pot is 500K ohm. This relationship provides a 50:1 audio voltage divider effect when the pot wiper is set at minimum voltage output. This is not trivial.
:
:Also note that the 1H5 tube's pin 7 ("high" side of C22) is the return point of the diode element in that tube which is used as the audio demodulator.
:
CV: one wire from ohm meter to chassis for ground other wire to pin 2 of 1H5 reading 10 ohms, S/B zero

8/13/2013 7:25:52 PMCV

Are you sure that you are looking at pin 2 and not pin 7?

8/13/2013 7:39:59 PMBob

:Are you sure that you are looking at pin 2 and not pin 7?
:
CV:Yes, Pin#2 about 10.1 ohms, I did pin#7,.5 ohms, I also took voltage reads-all just normal.

8/13/2013 8:06:25 PMCV

So, why isn't pin 2 zero ohms to ground?

8/13/2013 8:46:21 PMBob

:So, why isn't pin 2 zero ohms to ground?
:
CV: Removed tube, chassis ground to socket #2 1370 ohms,to #7 .6 ohms. tube pins 2& 7 together 10.4 ohms. I'll look in barn & find another 1h5 tube & measure ohms.,think I tried replacing tubes when problem 1st started. Its dark in Colorado now no lights in barn, I,ll post tomorrow.

8/13/2013 10:44:21 PMCV

Disregard my previous comment. I had mentally swapped the positions of pins 2 and 7. Pin 7 is connected directly to chassis ground. Pin 2 goes to C22 and the "low" side of the volume pot. 10 ohms from pin 7 to ground with the tube installed is probably OK.

8/13/2013 8:44:41 PMBill G.

::Are you sure that you are looking at pin 2 and not pin 7?
::
:CV:Yes, Pin#2 about 10.1 ohms, I did pin#7,.5 ohms, I also took voltage reads-all just normal.
:
Hi Bob,
I have a hunch here. Test your tubes.
When these 1 volt tubes come down with low emission they become microphonic. I am suspecting that the speaker sound is being picked up by a low emission microphonic tube and getting re-amplified.
Test them at the 1 volt filament voltage called out by the tube tester's directions.
No tube tester? There are things you can try.

Best Regards,

Bill Grimm

8/14/2013 6:29:27 PMBob

:::Are you sure that you are looking at pin 2 and not pin 7?
:::
::CV:Yes, Pin#2 about 10.1 ohms, I did pin#7,.5 ohms, I also took voltage reads-all just normal.
::
:Hi Bob,
: I have a hunch here. Test your tubes.
: When these 1 volt tubes come down with low emission they become microphonic. I am suspecting that the speaker sound is being picked up by a low emission microphonic tube and getting re-amplified.
: Test them at the 1 volt filament voltage called out by the tube tester's directions.
: No tube tester? There are things you can try.
:
:Best Regards,
:
:Bill Grimm
:
Bill;All tubes where tested & radios volume worked excellent, playing about 40 hours kinda like radio the volume kept increasing- guess at that point the 1H5 went south (bad). Found a couple of 1H5's (have couple of tube testers) used the one that tested best-replaced the 1H5 with the good testing one & the volume works just GREAT, not longer do I have to put cotton in my ears!Learned a lot on this one,only problem I distoryed the orginal volume pot & know have to find one that the double on/off switch will fit to, newer pots to small for swith to fit. Thanks

8/14/2013 6:35:18 PMBill G.

Thank you for the update! I like happy endings.

All the Best,

Bill

8/13/2013 8:46:10 PMClifton

CV,

Measuring from pin 2 of the 1N5 to ground will measure the filament resistance of that tube. 10 Ohms sounds close to the filament resistance of the 1N5. The voltage drop across the tube biases the detector diode to about 1.5 volts. Probably the only way to get the radio to turn all the way down is to remove the wire from pin 2 from the cold end of the volume control and ground it to the chassis. I don't know how this will affect the detector operation though.

Clifton

::Edd, you need to recall that, while the C22 cap's average impedance at audio AC frequencies may be in the 10K ohm range, the resistance of the pot is 500K ohm. This relationship provides a 50:1 audio voltage divider effect when the pot wiper is set at minimum voltage output. This is not trivial.
::
::Also note that the 1H5 tube's pin 7 ("high" side of C22) is the return point of the diode element in that tube which is used as the audio demodulator.
::
:CV: one wire from ohm meter to chassis for ground other wire to pin 2 of 1H5 reading 10 ohms, S/B zero
:

8/13/2013 10:40:31 PMCV

Yes, this was my mistake: for whatever reason I thought that pin 2 was the one that was connected directly to ground (actually, it is pin 7). I agree that 10 ohms is probably in the ballpark for the cold filament resistance.

8/25/2013 5:22:18 PMBob Z

Did you ever find the problem ?

8/25/2013 6:39:14 PMCV

Did you ever find the problem ?

-- See Bob's posting above dated 08/14/2013 18:29

8/26/2013 7:33:56 AMBob Z

:Did you ever find the problem ?
:
: -- See Bob's posting above dated 08/14/2013 18:29
:

Thanks, I missed that on.