7800 av help (no sound)

[Shawn]

The top of C10 is where you can tap for POKEY audio. C10 is to be removed also. From the pics it looks like it already is removed.

 

 

(MS PAINT 4 LIFE!)

Edited July 11, 2017 by Shawn

[SIO2]

The top of C10 is where you can tap for POKEY audio. C10 is to be removed also. From the pics it looks like it already is removed.

 

cheapo 7800 av.jpg

 

(MS PAINT 4 LIFE!)

 

So if I follow that correctly, you pick up pokey audio at the top of C10 and jump it to that via ahead of C14 and R6? Of course, I won't be able to do it exactly that way since that via is non-functional on this unit and that trace leading to C14 doesn't exist. But if that is the path, I can make it work.

Edited July 11, 2017 by SIO2

[CRTGAMER]

Looking at the OP and the second set of repair pictures, there are issues. Hopefully the excess heat did not kill any resistors or chips.

 

OP pictures too much heat melting the insulation of the wires, excess flux and where is the solder on the trace!?

 

Second set of pictures in the reply show solder, but way too much flux bleeding over to adjacent components.

 

Get a good pencil iron to pinpoint the solder where it is needed. Clean excess flux off board, then re solder as needed. If any traces are damaged run a jumper wire to act as the trace, have care on the heat!

[SIO2]

 

Trace to C10 was damaged so tracked it back. First jumped in before C14 but that produced pokey audio at much reduced volume relative to TIA even with R5 removed. So put R5 back and jumped in to South end of R5. Works to my liking now with both TIA and Pokey audio.

 

Thanks for the tips everyone. Got us on the road again.

Edited July 11, 2017 by SIO2

[Kaiju]

I learned a lot (op) from these mistakes. Again thank you everyone for the advice and tips.

[+DrVenkman]

I learned a lot (op) from these mistakes. Again thank you everyone for the advice and tips.

 

There's a lot of "art" to soldering and mod work on old PCB's. You have to do it enough to get a feel for how old solder melts and flows, how long you apply heat before you risk damage, etc. The only way to get that feel is to do it, but before you have the experience to get that feel, you risk damaging something. My suggesting to those first learning is always to get an old broken component out of a toy or old PC card and just practice melting solder, adding more, removing through-old components, etc.

 

Anyway, I'm glad the system in question was saved and is working! I still need to mod one of my 7800's, but I want to use one of Bryan's UAV boards and I don't have one handy. Maybe next week I'll order another.