What modern substitutions would you recommend for this amp

[Northwinds]

Cerwin Vega A-2200

200wpc @ 8 ohms
375wpc @ 4 ohms

I find it interesting that this amp almost doubles down. I had it set up in the garage using a APT Holman preamp, the amp is driving my CV E-712's out there. I moved it into the house using the Perreaux SA3 and driving the D9's. I noticed the bass was not tight at all and seemed to break up as volume goes up. Amp sounds muddy in the house whereas it did not seem to in the garage

Anyway, I would like this brought up to todays specs so I will be looking into replacing the big power caps also and maybe other things that could be out of spec. I was fooled by garage listening into thinking it sounded somewhat similar to the big Clair but even Debbie noticed the huge difference in SQ

If you can't see the numbers in the pic below, I will take the screen off again and write them down

EDIT: I see it looks blurry so I will post what they say

 

[Northwinds]

Top to bottom:

W9252
7604
7604
7604
7551

I have a feeling this is not right anyway and probably why it does not sound as good as it should. I have not checked the other 3 banks to see what is in them

Big caps are 19,000 MFD 75V

 

[Northwinds]

Here it is with the cover off, I took pics of both boards. So are these sort of like backplanes with independent control boards? Why is there 4 trim pots per board???

 

[Northwinds]

Looking at the pics, looks like one germanium on a control board was replaced at some point with a black thing? Maybe some other resistors or diodes have been changed also. Looking at the trim pots, I am guessing one set is for 120V and the other pair for 240V? Are those black things with the copper and hole that look like plugs where you hook up a meter to check bias?

Would possible replacement for the output transistors be MJ24/25s?

 

[WOPL Sniffer]

No, thats where you bolt them to a heat sink. Sell that thing and Don't look back.

 

[Gepetto]

Looking at the pics, looks like one germanium on a control board was replaced at some point with a black thing? Maybe some other resistors or diodes have been changed also. Looking at the trim pots, I am guessing one set is for 120V and the other pair for 240V? NO

Are those black things with the copper and hole that look like plugs where you hook up a meter to check bias? No those are transistors.

Would possible replacement for the output transistors be MJ24/25s?

Doubtful, looks like this amp uses TO-247 output transistors based on the hole pattern.

Looks like they borrowed a lot from Crown.

 

[Northwinds]

No, thats where you bolt them to a heat sink. Sell that thing and Don't look back.

It's my garage amp Perry, I don't plan to sell it but just want to make it safe for the long haul

What would you folks recommend for new output transistors then? The amp is from 1976 IIRC

 

[Northwinds]

Is this amp Full Comp? I see references to Full Symmetry/Complimentary

 

[JustMike]

Ron here is a couple of links and threads that would be a good place to start.
See if you can locate the service manual and schematic diagram.
These are great old amps.

http://www.audiocircuit.com/Home-Audio/Cerwin-Vega/A-2200-I

http://www.audiocircuit.com/Forum/Cerwin-Vega/8242/A-1800--A-2200--A-3000-Vintage-units

Jm

 

[Northwinds]

Thanks Mike, I will look at the links but not sure I will understand much that I read

There is 3 USA made CV amps that are pretty highly regarded (others were the 1800 and the 3000?), this is one of them but so few were made that they are relatively unknown. Even Ed was not aware of them. I can tell you this, even as it sits it is better than the Crown 300s I used to use in our old PA. It has 4 DC fuses and 1 AC fuse on the backside, separate gain controls also

EDIT: I see the second link confirms the 3 different Vega amps that are well liked

With 2 preamp boards, is this Dual Mono?

 

[oldphaser]

Top to bottom:

W9252
7604
7604
7604
7551

I have a feeling this is not right anyway and probably why it does not sound as good as it should. I have not checked the other 3 banks to see what is in them

Big caps are 19,000 MFD 75V

Ron,

Unfortunately the photos of the output transistors are a little blurry.

The (4) digit numbers you have above are the dates codes (the first 2 are the year, the second 2 are the week.)

More than likely the output transistors are something like RCA 65372? Perhaps they are RCA1B04's or RCA1B05's?
NOTE: Phase Linear did not have a good experience with the RCA1B05's as they didn't current share so well.
There is a chance if you replace these slower output transistors with the MJ series, the amplifier may oscillate.

Are the drivers RCA1B09's?

Ed

 

[oldphaser]

Here is a copy of the A-1800, A-3000 sales brochure.

Ed

 

[Northwinds]

Hey Ed, I popped another screen off another bank and I see:

1-4 top to bottom logo S (Seimens?) 2N6259

5th position bottom is RCA 65372

 

[oldphaser]

Hey Ed, I popped another screen off another bank and I see:

1-4 top to bottom logo S (Seimens?) 2N6259

5th position bottom is RCA 65372

Ron,

The RCA 65372's are more than likely a OEM part that was made for Cerwin-Vega. Much like the RCA66546 drivers made for Phase Linear that were actually a selected RCA410.
I can't find a cross for the RCA65372 anywhere on the internet. You may need to call C-V.

During the mid 1970's a lot of "selected" output transistors made by RCA were in the RCA1B0x series.

The RCA1B04's and RCA1B05's were used in many amplifiers during that era. Spectro Acoustics, Heathkit, Peavey, etc.

There was a RCA solid state devices data book that listed a 200 watt amplifier design (w/ schematics) in the back pages in an effort to sell these series of transistors.

Ed

 

[Northwinds]

Just read that sales brochure, if the specs are about the same as the 1800, this is a much better amp then I think most people give the brand credit for. You see that reference to unconditionally stable at any load? It looks like the A-2200 is a non metered version of the 1800. It has the same fuses that the 3000 shows on the faceplate. I thought it weird that I was cranking the shit out of it and it did not even get more then barely warm and the brochure explains why so thanks for that info also

 

[Northwinds]

I found a page with this:

My Cerwin Vega A3000-I came with RCA 65372 output transistors (28 of them) and many have been replaced with Motorola MJ15024 which are easy to find. I have recently replaced all of the transistors with new MJ15024 and have 12 good used ones left over if anyone would like them. I also have 13 good used 65372 if anyone would like these. Cheers, Ian

The above post was from 2007 on diyAudio

Now, could the big cans be upped to 22,000 100V versions? That protection circuit is kind of like McIntosh's Dynaguard the way it operates?

Just went to the CV official site and it appears that Gibson Guitars now owns the brand so I have to call them to find out about an amp transistor substitute? Wish me luck, took 2+hrs last time I called that number to trace down information on a 1993 Les Paul

 

[oldphaser]

I found a page with this:

My Cerwin Vega A3000-I came with RCA 65372 output transistors (28 of them) and many have been replaced with Motorola MJ15024 which are easy to find. I have recently replaced all of the transistors with new MJ15024 and have 12 good used ones left over if anyone would like them. I also have 13 good used 65372 if anyone would like these. Cheers, Ian

The above post was from 2007 on diyAudio

Now, could the big cans be upped to 22,000 100V versions? That protection circuit is kind of like McIntosh's Dynaguard the way it operates?

Just went to the CV official site and it appears that Gibson Guitars now owns the brand so I have to call them to find out about an amp transistor substitute? Wish me luck, took 2+hrs last time I called that number to trace down information on a 1993 Les Paul

Ron,

I saw the post on diyaudio as well. A lot of people just generically replace output transistors with MJ series devices without regard as to whether they will oscillate in their amps. Without the proper test equipment and knowledge, they will never know if their amplifier is oscillating. I would have like to known for sure exactly what the RCA 65372's were.

Have you joined the http://cerwin-vega-fans.com forum ?

Ed

 

[Northwinds]

Hey Ed, no I have not joined the CV Forum. I already belong to enough forums already. I have not even been really hitting the guitar forums for the last year or so. Between here and AK, that's enough

I don't know, I suppose you can always give it a look over when you visit again. I am pretty sure you will have fun looking it over. In the meantime, I moved it back into the garage for duties there. I will look around the 'net for more references and maybe find a schematic

 

[Northwinds]

eh, bit the bullet and joined. I posted asking for a sub for the RCA 65372 and see what comes up

 

[orange]

Did you check the eight big brown ugly block resistors as well?