Sunn Coliseum Salve Help/Ideas

[52 Bill]

I'd want to clean up that board a little, there is a burn mark, but because of all of the soot, I can't see how bad the burn is.

NTE stuff is not inherently bad, as long as it is used correctly. I've seen the wrong parts used to replace stuff before, so I'd double check the previous work before trusting it to be correct.

In case you didn't know it, TO-66 cases can be replaced with TO-220 case parts. The pin order and spacing is the same, all you have to do is to bend the base and emitter leads down in the correct spot. Cut off the collector lead and use the metal tab to make the collector contact.

[Enzo]

I think I may have TO66 sockets in stock, I'll check. But really, I think I would fish the broken contact out of the socket, and just solder a wire to the transistor pin where it sticks through.

[TigerAmps]

"Does the board have the number 20-0026 on the back?"

Yes it does ... It is different from the image posted above (post #4).
I posted a picture of the actual board from the amp above in post #3.
I think I'm just going to have to go thru the board and mark up a copy of the schematic with the changes.

I was hoping that someone who used to service Sunn amps back in the day may have the full set of schematics
including the changes over the years.

I will measure the resistors/caps and test all the transistors over the next couple of days to see what the damage is.

[loudthud]

Does the board have the number 20-0026 on the back?

The resistor that is soldered to the diode legs in the middle of the board seems to be the bias adjustment. I have a Coliseum Bass dated December 1970 that has no pots on the board. It's layout is slightly different.

Attached is the layout for the 20-0026.

[TigerAmps]

Thanks for responding Bill!

The previous owner said it "blew the fuse" (despite the fact it has a circuit breaker).

Upon inspection:
1) the meter was physically broken.
2) One of the to-66 transistors was not in the socket
3) one of the to-66 sockets connections was broken off.
4) One of the .33 10W resistors was open.
5) the wires to the board were all removed and some were cut (wanker!)

I attached pictures of the actual board!

So far I did the following:
1) replaced the bridge rectifier
2) checked the main caps and they were "good" (not open nor shorted)
3) replaced the .047 caps in the power supply (primary side)
4) replaced the .33 10W resistors that was open.
5) disconnected the +/- 50V from the 2 power caps going to the amp circuitry
6) disconnected the wire feeding the meter circuit
7) fired it up and tested the power supply which measured +/- 52V on the caps. (at least the PS works!)
8) tested the output transistors (all RCA 2n3055) and they all checked out with the diode test

Finally pulled the board and started looking it over.
I noticed half the transistors were replaced with NTE stuff (which always scares my - especially around Halloween!)

So I need to:
1) go over the board (and was looking for the 20-0026 board schematic)
2) order to-66 sockets and the 2N3441's

If I can not get the to-66 sockets, considering the to-220 type transistors.




I hope that sheds some light on what the state of the amps is ...

[52 Bill]

What do you mean by DOA, no power on, power but no sound?

This is really just a basic power amp so it shouldn't be that hard to fix. As for the 2N3441 replacements, are the ones in there bad now? Have you looked at TO-220 case transistors?

[TigerAmps]

I have a Sunn coliseum slave. The prior owner went in and replaced the drivers (2N3441's) with NTE's and a few other things with NTE.
The schematic I found does not match the board (20-0026 D) exactly. For example: The schematic shows 2 variable resistors yet the board only
has one. The amp dates to 1971. Also, anyone every replace the 2N3441's with anything else? It came to me DOA and I'm trying to bring
it back to life. I have attach a picture of a similar board and the diagram I currently have which is close, but not exact.

One of the BC107's was replaced with an NTE and a few other transistors.
As for the power section, one of the .33 ohm 10W resistors was open and all the output transistors meter out fine.
Also, one of the TO-66 transistor sockets needs to be replaced (one of the connection leads is broken off).

Any ideas or info is greatly appreciated!