Ulitmate Chorus DSP - no sound, but powers on

[juststrummin2]

My DSP is not producing any sound. Everything powers on, but nothing, not even a hum. Opened the case and looked at the CB. Some pretty nasty burned areas. However, the diodes appear to measure OK with a volt meter. However, I am not an electronics expert so I may not be measuring them correctly.

I don't see any problems with the soldering on the back of the CB.

I have attached a pic of the burned areas. Any thoughts, suggestions?

[52 Bill]

Any thoughts, suggestions?

Welcome. The discolored areas are from heat created by the zener diodes. This is fairly normal.

Start by checking the speaker and the break jacks if the amp has them. Is this a stereo amp?

[juststrummin2]

Welcome. The discolored areas are from heat created by the zener diodes. This is fairly normal.

Start by checking the speaker and the break jacks if the amp has them. Is this a stereo amp?

This is a stero amp. Can you give me some tips on how to check the speakers. I don't know what a break jack is, so if you could briefly explain it would be appreciated. Thanks

[juststrummin2]

Welcome. The discolored areas are from heat created by the zener diodes. This is fairly normal.

Start by checking the speaker and the break jacks if the amp has them. Is this a stereo amp?

This is a stereo amp. Can you give me some tips on checking the speakers. I don't know what a break jack is, so if you could briefly explain, that would be terrific. Thanks

[52 Bill]

This is a stereo amp. Can you give me some tips on checking the speakers. I don't know what a break jack is, so if you could briefly explain, that would be terrific. Thanks

I just looked up the schematic for your amp, you have two different FX loops, one mono and one stereo. Each one has an internal switch that is normally closed to bypass the loop when there are no cords plugged into them. Sometimes the switch becomes oxidized and no longer closes the connection and therefore kills the sound of the amp.

Take a spare guitar cord and plug one end into the FX send and the other end into the return jack. If the sound is restored the return jack needs to be cleaned.

For the speakers, as the amp is stereo the chances that both are dead is quite unlikely, so I'd suggest that you just check the FX loop jacks. I you want to check them the fast test is to unhook one of the wires going to the speaker. Then take a 9 volt battery and touch the two battery terminals to the the two speaker terminals. If the speaker voice coil is ok, there will be a loud thump from the speaker.

[soundguruman]

What happens is that the voltage regulator, to supply low voltage, uses ceramic resistors and zeners, that get the board and circuit tracks quite hot.
Over time, the solder connections and circuit tracks degrade from the heat and fail.
And so usually you can take the board out, bypass the bad tracks with new wire, and re-do the solder connections.
Also, its a really good time to replace all the jacks on the front of the amp. Those jacks need to work 100% because the audio travels "through" the jacks. If the jack is old and oxidized it will stop the amp from working.
Then when you put it back together, coat both sides, chassis and the metal bar, with fresh heat sink compound.

[soundguruman]

check the speakers by touching a 9 volt battery to the terminals. this should make the loud speaker "pop." That's a good test.
when the speaker moves in and out, it should move freely. If it scrapes, or if it does not move, it's blown.
Take the speaker out and check the movement of the cone, by moving it in and out with your hands.
Does it scrape? or is it free to move in / out, without interference?
A speaker that scrapes when it moves is bad. It will also sound bad, if it works at all.