Who Wants to Help Me Fix an Amp?...

[Coda]

I bought an amp several months ago: and Acoustic 134 (essentially a solid-state Super Reverb). I got it for next to nothing. Up until recently it has worked 100%...except every now and then the volume would drop when playing through the reverb channel. A swift tap on the top of the amp, just above the input/volume control would immediately remedy the problem. Yesterday the volume cut out completely, and no amount of hitting has brought it back. I still have the normal channel...but solid-state + no reverb =...eh. The symptoms lead me to think that there is a loose connection, probably involving the volume pot.

Any tips on working on amps? I know that tube amps are far more en vogue, especially when it comes to tinkering, but any tips would be appreciated. I plan on pulling the chassis out this weekend and checking under the hood. Hopefully a shot of CRC will fix the issue. It usually does...

 

[thesmokingman]

1970s solid state should be fairly straightforward to work on ... recap the electrolytics as a start ... also provide a link to the schema please and thank you

 

[Coda]

1970s solid state should be fairly straightforward to work on ... recap the electrolytics as a start ... also provide a link to the schema please and thank you

https://drive.google.com/file/d/10jtmK4aon6BBKO9LOe8hLIWL63YTu2Q1/view?usp=sharing

This is a scan of the manual. There is a lot in here, but its pretty cool to look through. The only error I have found is on the last page: it reversed the speaker specs of the 134 (4 10 inch Eminence), and the 135 (2 12 inch Oxford). This manual is also a tad younger than my amp. This manual is probably 1974-1975. I believe my amp is a 1972.

Tapping on it bringing the sound back also points toward some sort of loose connection.

Have you looked inside?

That's my plan for Saturday. It most likely is a connection (I hope). The place I bought it from runs all their stuff through a repair shop, and I imagine (or maybe hope) that the recap was already done. If its not a loose connection, its probably the flux capacitor...

 

[fig]

https://drive.google.com/file/d/10jtmK4aon6BBKO9LOe8hLIWL63YTu2Q1/view?usp=sharing

This is a scan of the manual. There is a lot in here, but its pretty cool to look through. The only error I have found is on the last page: it reversed the speaker specs of the 134 (4 10 inch Eminence), and the 135 (2 12 inch Oxford). This manual is also a tad younger than my amp. This manual is probably 1974-1975. I believe my amp is a 1972.


That's my plan for Saturday. It most likely is a connection (I hope). The place I bought it from runs all their stuff through a repair shop, and I imagine (or maybe hope) that the recap was already done. If its not a loose connection, its probably the flux capacitor...

Remember to tap with something not quite as conductive as say....your finger. I like [wooden] skewers, but not the ones with teriyaki sauce all over them.

Edit: added "wooden" for clarity

 

[Coda]

Remember to tap with something not quite as conductive as say....your finger. I like [wooden] skewers, but not the ones with teriyaki sauce all over them.

Edit: added "wooden" for clarity

I usually use a pencil, eraser-end first. People usually say “ow!” when I use the point…

 

[Paradox916]

Remember to tap with something not quite as conductive as say....your finger. I like [wooden] skewers, but not the ones with teriyaki sauce all over them.

Edit: added "wooden" for clarity

Teriyaki is Japanese for magical tone… you said “Make it sizzle!”

 

[fig]

Teriyaki is Japanese for magical tone… you said “Make it sizzle!”

Indeed. [ looks unconvincingly like it was intentional ]

 

[dgrainger]

Chopstick it. Get it under a magnifying glass and look for cold solder joints. It's just a really big pedal.

 

[Feral Feline]

The sporadic thump to get it working and then it quitting altogether made me think cracked solder connection, too, as degrainger said. I also espouse using wooden chopsticks, cause if you use a pair you can pick things up (like a dropped cap in the chassis, etc)…

Good luck!