Dadgummit! 2275 MPX board recap, now no radio...

[Briant8]

Hi all!
I've been following along with both thxdave and Steven Tate's threads as it seems that we are all currently recapping a 2275 (how do you guys insert those cool short blue links? Was going to link to those threads and the parts list, but it comes up as the big long URL address...)
I've successfully completed the PS, preamp/tone, phono, the two main amps and Dolby boards. (I was a good boy and successfully function tested after each step)
However, after redoing the MPX board (man, what a PITA to get under!) I get no radio output. All other inputs/outputs work except AM/FM output. The tuning meters seem to be working as the tuning dial moves, so I'm guessing that it's getting reception, but just no output.
I used the parts list that Dave posted (see, it would be nice to put one of those cool links in right now!) with a few substitutions. I did also unsolder the pins at J307, J317 and J322 to get a little more slack to get under there, but that all went back together without much ado.
Ok, hit me!
And as always, thanks in advance for the sage advice

 

[Beamer302]

You might want to go over your work and check for bad solder joints, broken traces and pads and check for loose components (capacitors). I sometimes find that when I go over my work I wiggle a capacitor and sure enough it might be loose or lifting a pad or not even soldered. I have had this issue too. I would check the voltages on the H321 chip and maybe some transistors to see if the board is getting power. Be careful not to short anything out. Black probe to ground on the DVM. Red to each leg of IC (H321). Make sure the Mute button isn't on. It's odd that the AM doesn't work. Hopefully it is something simple.

 

[catrafter]

No AM or FM usually means no 13 Volt power supply. You may have shorted it out by pinching a wire somewhere, or it may have broken off at a wire wrap. Trace the wire from J806 on the power supply.

Tom

 

[Beamer302]

Does the tuning indicator (pointer) light up when the selector switch is turned to AM and or FM position ?

 

[Briant8]

Thanks for all of these great ideas! I'll check them when I get back home on Saturday.
I did check all of the solder joints that I was able to see and even used a dental mirror. I touched up a couple that looked flaky.
I'm almost decided to commit the unforgivable and take the dang board completely out so that I can examine it.
It's so hard to work under...

Does anyone have a schematic with voltages? The service manual isn't very forthcoming with that on this board that I can see.
The board is getting power, I just don't know if it's the correct power.

Where does signal come off of this board?

I will check the pointer lamp, it may actually be out. I haven't gotten to re-lamping him yet.
(And it's been a couple of weeks since I went digging inside, I got a little frustrated after this and wisely put him aside lest I Chuck him off the balcony!)

Thanks again, for the tips. I'll keep you posted!

 

[Richs_Trains]

Wish I had a balcony to chuck things off of

 

[Steven Tate]

You know I'm coming from the standpoint of shallow experience, but Catrafter says look for 13v first. If I'm reading the schematic correctly, it looks like the 300 board gets 13.4v at J304. A good starting point might be to test the voltage at that point. If it is absent at that point, go back to the PS, J806 and look for 13.4v. If you have power at J304, it's time for some more suggestions from the guys who know what they are talking about.
Steve

Edit - I have my 2275 open and tested for DC at J304 and indeed got 13.4v. So this is a starting point.

 

[catrafter]

Dr. Tate is correct, 13V at J304.

Tom

 

[Briant8]

Can't wait to get home and check it out!

 

[Golanr]

Can't wait to get home and check it out!

Hi Brian,
I'm now having the exact same issue. After recapping the PS, Preamp, Phono amp and both Power Amps, all inputs are working besides AM/FM. In my case even the tuning meters don't respond as the tuning dial moves. Did you manage to fix it? if so, how?

When I get home, I'm definitely going to test @catrafter & @Steven Tate suggestions.

Thank you

 

[Briant8]

Hi Brian,
I'm now having the exact same issue. After recapping the PS, Preamp, Phono amp and both Power Amps, all inputs are working besides AM/FM. In my case even the tuning meters don't respond as the tuning dial moves. Did you manage to fix it? if so, how?

When I get home, I'm definitely going to test @catrafter & @Steven Tate suggestions.

Thank you

Oh my gosh, that’s been a while back!
I can’t honestly say if I remember. I don’t think I did get this resolved.

I’m sure I put it aside and it’s gotten buried under the to-do pile.

We’ve moved since then and I’m not even sure where that unit is st the moment... :-/

Please keep us updated.

Brian

 

[Golanr]

Have my own post on this but trying to help anyone checking this one. I'm getting 3.4V at J806 on the power supply. It is supposed to be 13.4v. It then feeds the FM MPX board and I'm assuming also the AM board. Tracing to H804, I get the same on the Emitter of the new MJE15030G and 3.76V at the base.
I traced the cable from J806 to the the star splitter in the bottom. I disconnected it from the splitter and tested again. 13.66V which is close enough. So I'm assuming the problem is further down the line. The question is, which of the cables leaving the splitter is connected to the board causing the issue. More tracing is needed...I will continue this on my post http://audiokarma.org/forums/index.php?threads/2275-recap-more.815900/

 

[PooPoo]

I’m not getting any voltage at j806 on my 2275 can anyone tell me what I need to do to get my radio working?

 

[ivandezande]

I’m not getting any voltage at j806 on my 2275 can anyone tell me what I need to do to get my radio working?

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