Another 2517 low receive issue

[Hawkeye351]

I read on the Galaxy updates page that if a 2517 has low receive audio, then cut the red wire beside CN13 on the switchboard and route that wire to R90. They claim R90 is on the corner edge of the main board, but this R90 in this 2517 is next to the balanced modulator. They claim this issue comes from the NF and Roger beep being on at the same time will drop the constant 8v needed to provide receive voltage. I checked that red wire beside CN13 on the switchboard and it has a constant 8v on it, so I didn't move it. Should I? And if so, where should I route it to for the constant 8v? Straight to the 8v regulator, or to the electrolytic cap next to the pll which has a constant 8v?

 

[Hawkeye351]

I have the RF gain wide open clockwise.

 

[Hawkeye351]

RF gain centered:

Connector beside R233:
R1 - 3.20
R2 - 1.42
G - 0

The leads on the RF gain control correspond also with these numbers.

 

[brandon7861]

That looks good too, RF gain pot is working fine.

If the voltage isn't sagging, I wouldn't move it.

I will have to think about what to check next. Hopefully the snow holds off, because once it hits, I'm outside until I go home

 

[brandon7861]

If you were going to check the electrolytic caps around the audio amp, you don't really have to pull them. Electrolytics almost always fail open, so just touch another cap across their contacts one by one and see if the audio comes alive.

 

[Hawkeye351]

I honestly believe now that the receive is there, just the volume is low, as though the volume control isn't working. I checked it and it tests as a 1k ohm, which it should be.

Getting the right signals on all my locals, and skip, just the volume has to be jacked almost wide open to hear anyone.

 

[brandon7861]

schematic shows a 50KA for the volume pot. What did you measure as being 1k?

edit: Maybe someone swapped it with 1k and thats whats loading down the signal??

 

[Hawkeye351]

My bad, the volume and squelch pots are 50k ohm each, sorry about that brau. It's the RF gain and Mic gain pots that are 1k ohm each.

 

[brandon7861]

I would also touch a cap across the emitter bypass at Q16 C38 and the output decoupling cap C20 on the noise filter board to see if either of those went dry.

...and here comes the freezing rain, I gotta go salt sidewalks

 

[Hawkeye351]

Ok, be careful out there. I'll look into these until tomorrow and give an update. Thank you brau...

 

[Hawkeye351]

Yanked out and tested the following (replaced all 4 anyway):

C243 (tested fine with good ESR).
C182 (tested as right UF but had high ESR, over 70 ohms).
C179 (tested fine with good ESR).
C175 (tested fine with a slightly high ESR).

Q44 (tested as a BJT but had over 300 HFE. Replaced anyway.

Outcome:
Same results, receive is there, but have to crank volume wide open to hear anyone comfortably.

I did notice that pin 10 of the audio IC (7222ap) has dropped to around 10.32v with volume wide open. Turn it down halfway and pin 10 comes back up to over 11v. Also, at half volume it's smooth audio but just low, crank volume wide open and it makes a frying hissing noise and then pin 10 drops below 11 volts. I noticed all this behavior last night before replacing anything.

Might need to pull the old signal tracer out and prod around the audio IC.

 

[Hawkeye351]

If I run my finger across C184 and C182, the receive volume jumps up, gets fuzzy and then drops back down until I run my finger across them again. C182 I've replaced, gonna replace C184 and try that. I may even yank out the 7222ap IC and put in another one. Not sure if it's that 7222ap or not though, because I think the transmit audio goes through that IC also and I've got great transmit audio, so I'm a little confused right now.

 

[Hawkeye351]

Does transmit audio go through the 7222ap IC? If not, then the IC may be the issue. Transmit audio is great according to my locals.

 

[BayouRadioAmplifier]

I have been reading this thread here. I have a local with a 2517 with
maybe the same problem. it was a few weeks ago. He said his 2517 has
weak receive signal. so can you see a high level S-meter reading
and with low audio? is it low audio, or bad receiver problem?

I will cell phone text this guy and see if he wants to come over for this repair.

 

[Hawkeye351]

My issue is low volume. The receive signals look right on the meter, just low volume. Transmit audio is great though.