Hi guys I need some help on this problem.
First I'm not that knowledgeable and pretty frustrated.
the problem is that when I press the bcb switch part way in there is reception and when it's all the way in the signal strength drops significantly especially from 800 to 550kc.note I am using a 1r5 in place of 1l6.
Also the sets been recapped and I gave the switch assy a good clean and sprayed with deoxit.
I was looking at the schematic fig 16 of the military manual which shows the bcb circuit but don't know what the box symbol is as opposed to that other polygonal one.
I don't have a 1l6 so I'm not sure if this is due to the 1r5, if it is this issue may be mute.
Any advice?

many thanks JIM

What does "sia" mean?

Here is the schematic: http://www.transoceanic.nostalgiaair.org/h-500.htm I don't see the box or polygon. Can you help us locate them?

Does the set work properly on the shortwave bands? If so, and from what you describe, everything would point to the BC switch. contacts.
Doug

:Hi guys I need some help on this problem.
:First I'm not that knowledgeable and pretty frustrated.
:the problem is that when I press the bcb switch part way in there is reception and when it's all the way in the signal strength drops significantly especially from 800 to 550kc.note I am using a 1r5 in place of 1l6.
:Also the sets been recapped and I gave the switch assy a good clean and sprayed with deoxit.
:I was looking at the schematic fig 16 of the military manual which shows the bcb circuit but don't know what the box symbol is as opposed to that other polygonal one.
:I don't have a 1l6 so I'm not sure if this is due to the 1r5, if it is this issue may be mute.
:Any advice?
:
:
:many thanks JIM

Is SIA meaning STA, as in 'stations'? The 1R5 should be OK on the broadcast band, but will operate poorly on the higher SW bands.
Deoxit is good stuff, but it can't perform miracles. The switch contacts might have a hard, black oxidation on them. You may have to dismantle the switch and rub the deposit off gently. The contact terminals may be worn and sprung, you may need to bend them together slightly for contact. When actuating the switch, you should see them move ever so slightly, this means that they are touching the contact stem.
Take your time and be careful, the coil rack area and winding leads are very delicate.

: Is SIA meaning STA, as in 'stations'? The 1R5 should be OK on the broadcast band, but will operate poorly on the higher SW bands.
: Deoxit is good stuff, but it can't perform miracles. The switch contacts might have a hard, black oxidation on them. You may have to dismantle the switch and rub the deposit off gently. The contact terminals may be worn and sprung, you may need to bend them together slightly for contact. When actuating the switch, you should see them move ever so slightly, this means that they are touching the contact stem.
: Take your time and be careful, the coil rack area and winding leads are very delicate.

I would think that "S1A" would mean SWitch 1, section A.

Lewis

:What does "sia" mean?
:
:Here is the schematic: http://www.transoceanic.nostalgiaair.org/h-500.htm I don't see the box or polygon. Can you help us locate them?
:
:Does the set work properly on the shortwave bands? If so, and from what you describe, everything would point to the BC switch. contacts.
:Doug
:
::Hi guys I need some help on this problem.
::First I'm not that knowledgeable and pretty frustrated.
::the problem is that when I press the bcb switch part way in there is reception and when it's all the way in the signal strength drops significantly especially from 800 to 550kc.note I am using a 1r5 in place of 1l6.
::Also the sets been recapped and I gave the switch assy a good clean and sprayed with deoxit.
::I was looking at the schematic fig 16 of the military manual which shows the bcb circuit but don't know what the box symbol is as opposed to that other polygonal one.
::I don't have a 1l6 so I'm not sure if this is due to the 1r5, if it is this issue may be mute.
::Any advice?
::
::
::many thanks JIM

::What does "sia" mean?
::
::Here is the schematic: http://www.transoceanic.nostalgiaair.org/h-500.htm I don't see the box or polygon. Can you help us locate them?
::
::Does the set work properly on the shortwave bands? If so, and from what you describe, everything would point to the BC switch. contacts.
::Doug
::
:::Hi guys I need some help on this problem.
:::First I'm not that knowledgeable and pretty frustrated.
:::the problem is that when I press the bcb switch part way in there is reception and when it's all the way in the signal strength drops significantly especially from 800 to 550kc.note I am using a 1r5 in place of 1l6.
:::Also the sets been recapped and I gave the switch assy a good clean and sprayed with deoxit.
:::I was looking at the schematic fig 16 of the military manual which shows the bcb circuit but don't know what the box symbol is as opposed to that other polygonal one.
:::I don't have a 1l6 so I'm not sure if this is due to the 1r5, if it is this issue may be mute.
:::Any advice?
:::
:::
:::many thanks JIM

http://www.transoceanic.nostalgiaair.org/index.htm#h500

hi doug
on the above link check the mil manual for r-520 then see figure 16. the notation for the switch is at the bottom of the figure "SIA BC" not sure what the SIA means.
The set works but just barely on the upper band which is expected with the 1r5

Oh, OK - thanks.

That 209-page Army tech manual for a T/O is something else. I'd love to know how much the government paid Zenith to develop that manual! Yikes.

I wonder what the U.S. Army used T/Os for in the 1950s (the date on the tech manual). I can only think of morale radios. If they were passed out to the troops, how many of them were ever turned back in?
Doug

:
:hi doug
:on the above link check the mil manual for r-520 then see figure 16. the notation for the switch is at the bottom of the figure "SIA BC" not sure what the SIA means.
:The set works but just barely on the upper band which is expected with the 1r5

On broadcast band the !R5 is fine. Make sure you have good continuity in your wavemagnet. Being a tuned circuit the BC band needs that to be working. Remember also the wavemagnet will null signals if not turned correctly. Rotate the wavemagnet or the entire radio for best reception. I thought mine was dead also on part of the band until I started rotating the radio.

:On broadcast band the !R5 is fine. Make sure you have good continuity in your wavemagnet. Being a tuned circuit the BC band needs that to be working. Remember also the wavemagnet will null signals if not turned correctly. Rotate the wavemagnet or the entire radio for best reception. I thought mine was dead also on part of the band until I started rotating the radio.

Thanks Joe and everyone I'll try to get a better look at the contacts and recheck the wavemagnet.
I'll post again any follow up.

thanks to all
JIM

::On broadcast band the !R5 is fine. Make sure you have good continuity in your wavemagnet. Being a tuned circuit the BC band needs that to be working. Remember also the wavemagnet will null signals if not turned correctly. Rotate the wavemagnet or the entire radio for best reception. I thought mine was dead also on part of the band until I started rotating the radio.
:
:
:Thanks Joe and everyone I'll try to get a better look at the contacts and recheck the wavemagnet.
:I'll post again any follow up.
:
:thanks to all
:JIM

Does that model have a selenium rectifier? My T/O (L series) would work on some BC stations and fade out completely on others after a minute or two. The voltages were a little low after a check. The SW seemed to work fine at that time also.

I changed the rectifier with a diode and dropping resistor and it works fine now.

Could that be your problem?

Hi Jim,
Neither Selenium rectifier, wave magnet nor 1R5 has anything to do with this problem.
It sounds like your switch is out of adjustment. The metal connections that make the switch are going past the contacts.
Using an ohm meter and schematic you ought to be able to track down the switch section that has the problem. Once located you may be able to find out how to adjust it back.
The band switch mechanism is quite complicated on this so don't work on it whne you are tired.

Best Regards,

Bill Grimm

Jim,

Another thing. Since you are using a 1R5 instead of the infamous 1L6, you may have to remove pin 5 of the 1R5. Pins 1 and 5 of the 1R5 are tied together internally. Not so in the 1L6. With the connection of 1 and 5 being made by the 1R5, may be upsetting the bias on the tubes. The bias circuit is quite elaborate in a TO. I have a Zenith AM only radio that had a bad 1L6 so I used a 1R5 but had to remove pin 5 to get it to work properly. If you do remove pin 5 from a 1R5, I might suggest using a Dremel tool with a cutoff disk instead of cutter pliars as the pliars may crack the tube base.

Radiodoc
******************

:Hi guys I need some help on this problem.
:First I'm not that knowledgeable and pretty frustrated.
:the problem is that when I press the bcb switch part way in there is reception and when it's all the way in the signal strength drops significantly especially from 800 to 550kc.note I am using a 1r5 in place of 1l6.
:Also the sets been recapped and I gave the switch assy a good clean and sprayed with deoxit.
:I was looking at the schematic fig 16 of the military manual which shows the bcb circuit but don't know what the box symbol is as opposed to that other polygonal one.
:I don't have a 1l6 so I'm not sure if this is due to the 1r5, if it is this issue may be mute.
:Any advice?
:
:
:many thanks JIM

In T/O's you can replace the 1L6 with an 1R5 without cutting any pins. I believe that to be an accurate statement. In other models like a G503, you must remove a pin.