Sunn Coliseum Salve Help/Ideas

[shiner555]

Awesome!! For some reason I can't post the pix....here is a link to where they are on facebook.

https://www.facebook.com/Goddard.Mus...type=3&theater

PCB is 20-0026d

I'm looking to verify the values of the blown resistors. R217, R218, R216, R215.

It looks like R218 is the one that caused the fire. It's directly tied into Q5. It's strange as Q5 tests out just fine......I'm going to go and replace all the caps and test all of the transistors on this PCB as well. Also, I'll verify all output devices. They are only a couple of years old, so they should be good, but also could have been the cause of the problem. Then again, if Q6-8 would've went I also would've expected Q5 to go, but maybe not do to how R218 is tied into the output devices.

How did you sub's work for the small transistors on the board? Any issues?

Thanks!!

[TigerAmps]

I have both a coliseum slave and bass (both amps).

I did refurbish the slave (I have pictures and know the values) - the bass is still a work in progress (I just have not gotten back to it).

Can you post a picture of the board? The differences are minor mostly a cap and the 4 diodes in the middle of the board.

Check everything on the board probably will require a complete rebuild due to the age.
Also - if the main supply caps are original and you want to keep the amp, consider replacing them as well.
When I got one of the slaves, one of the main supply caps was open and it just output 60 cycle hum as a loud volume (not fun).


Any questions on component values - just ask or send a PM

The re-furbished board:

[glebert]

Oh man!! Yes, ok! I know who this is! Nice to run into you on here Greg. It's Jason/Nirv. Yeah, the amp was a flame/smokeshow. I'd already be on my way to repair if the schematics I have matched the PCB's. Hopefully this thread will shed some light. I also found Conrad Sundholm online and threw him a hail mary email for possible further info.

Figured it was you I'll send a PM.

[shiner555]

Old friends of mine from MTU, saw pics of the carnage on FB.

Oh man!! Yes, ok! I know who this is! Nice to run into you on here Greg. It's Jason/Nirv. Yeah, the amp was a flame/smokeshow. I'd already be on my way to repair if the schematics I have matched the PCB's. Hopefully this thread will shed some light. I also found Conrad Sundholm online and threw him a hail mary email for possible further info.

[glebert]

Heh.....maybe..... Were you there?

Old friends of mine from MTU, saw pics of the carnage on FB.

[shiner555]

Odd question, but are you with the band Goddard? I just know they had one burn up on Sunday too.

Heh.....maybe..... Were you there?

[glebert]

Oh man!!! This thread may very well save me. I had my 70's coliseum bass go up in flames at a gig this past Sunday. When I compared the driver PCB 20-0026D to the avail schematics, it didn't match and had me really worried I wasn't going to be able to figure out the correct parts to put back in. TigerAmps, did you ever verify the resistor values you replaced?

Odd question, but are you with the band Goddard? I just know they had one burn up on Sunday too.

[shiner555]

Oh man!!! This thread may very well save me. I had my 70's coliseum bass go up in flames at a gig this past Sunday. When I compared the driver PCB 20-0026D to the avail schematics, it didn't match and had me really worried I wasn't going to be able to figure out the correct parts to put back in. TigerAmps, did you ever verify the resistor values you replaced?

[TigerAmps]

Update -finally got back to this amp ...

Re-furbished the board and checked the output transistors!
I finally connected the board and fired it up today with the meter circuit disconnected and it works - yeee - haaa!

The meter is damaged beyond repair.

This is going to be a long shot but: Has anyone found replacement meter for the Sunn Coliseum Slave?
Newark.com lists VU meters, I was wondering if anyone in the forum has used any of them or have another source for something that would fit (from experience)?

If not I will pull the meter, measure it and start searching ...

Thanks in advance!

[R.G.]

Don't start it up on a variac. Start it up on a light bulb limiter. Very different kinds of protection.

[TigerAmps]

Will Do! Thanks ...

[loudthud]

If you start up the amp with a Variac, don't connect any kind of load. The output will go to the negative rail until the incoming line Voltage reaches about half the intended value. It's best to use a Variac that had some kind of current meter. Watch the current and stop if the current goes too high. There will be some current required to charge up the filter caps so it's hard to say what too much is. A light bulb limiter is really a better idea because it automatically limits current, or use both.

The light should flash bright then dim to a dull orange. Check the Voltage at the output for near zero Volts.

[TigerAmps]

That is pretty much where I am; not taking anything for granted!

I am checking all the resistors, diodes, replacing the burnt/charred components and the orientation of the transistors.

Question:
If I start this up on a variac, what do I look for?
Any recommendation for a procedure to follow?

I only ask because this would be the first "near complete" rebuild I have attempted.

Thanks ...

[R.G.]

Given the degree of damage you noted, I think you would be wise to count on substantially remanufacturing it: either replace or measure and verify every component. The hours you save will probably more than pay for component costs.

[TigerAmps]

Quick Update:

I checked over the board and there were minor difference such as
1) a few components were in different locations
2) the bias pot was replaced with a 1K resistor
3) One of the C206 or C207 had a different value (I don't remember which)

The resistor that burned was R221 (one of the 150 ohm resistors). The board currently has a 1.5K 1/2 watt resistor (which is wrong)
in it's place (if you look at the picture of the board). However - R220 is a 150 ohm 1 watt resistor on the board and it looks original so
I was going to replace R221 with a 150 Ohm 1 watt resistor as well.

Also, Q204, Q205, Q206 and Q207 all appear to be blown (at least one is shorted, one is open). I plan to replace them all as the BC107 or shorted and the others are questionable (NTE); I need to pull them and check them all; At this point think of replacing them anyway to make sure we start off on a solid foundation.

I was thinking of the following replacements:

BC107B -> Still available (Fairchild BC107B)
2N4250 -> 2N3906 or 2N5401
2N3440 -> Still Available (Central Semiconductor 2N3440)
2N4888 -> 2N5401

If anyone has any better suggestions or recommendations for the transistor substitutions, please let me know ...
Also, someone please confirm these choices make sense (especially the 2N4250).

Thanks!