Looking for readable Marhsall 2100 SL-X preamp schematics

[qmp audio]

Looking for readable Marshall 2100 SL-X preamp schematics.

I found a few gifs online,  but they're to low res to make out the values.

I'm looking for a readable version of this:
http://www.prowessamplifiers.com/schematics/Marshall/2100slx_pre.pdf

Thanks for any help!

 

[analogguru]

Did you try this ?:

http://www.drtube.com/library/schematics/69-marshall-schemas#JCM900SLX

Google is your friend.....

 

[qmp audio]

Did you try this ?:

http://www.drtube.com/library/schematics/69-marshall-schemas#JCM900SLX

Google is your friend.....

Yes I googled that already.  That's the one i'm referring to that is too small to read.... a lot of the values are too pixelated.  looking for something higher res,  or a nice scan.  Thanks.

 

[analogguru]

Yes I googled that already.  That's the one i'm referring to that is too small to read.... a lot of the values are too pixelated.

I don´´t know, but I can determine all values...

looking for something higher res,  or a nice scan.  Thanks.

Good luck.....

 

[PRR]

> values are too pixelated.

It reads fine here. 1M, 68K, 2K7, 220K....

It IS bigger than my monitor. Maybe you have an auto-resize feature mushing it down to fit your screen?

 

[qmp audio]

i was having trouble making out BR3,  which the one that was in the amp has no markings.  2w0-01 is what i believe but can't find anything at mouser w/ that #.    I was going to use 4x 1N4007 as a replacement,  but am not sure if the 1A rating is sufficient.

I guess the better question to ask here is that.

 

[analogguru]

Maybe you have more luck finding a:

W005, W01(M), W02, W04, W06, W08, B40C1000, B40C1500, B80C1500 or B80C1500.

 

[PRR]

> making out BR3

It powers tube heaters. It has to be less than 18V peak stress. 50V is the smallest you can buy, 1000V is cheap also.

That plan is a maze and may not be complete. I can not tell if it is one or three heaters, at 6V or 12V. Worst-case, it might be 0.9 Amps. You would think a 1 Amp part would do. In fact that might be not-enough for looong-term reliability. Perhaps the designers made the same mistake?

A 3A or 5A 400V bridge rectifier is, IMHO, cheaper than wracking eyes and brains. Too-big is only a few pennies wasted; almost big enough is a future gig spoiled.

 

[qmp audio]

Thanks for looking.  Yes its heater for preamp valves 1-3.    .9A is what i was thinking too.

Perhaps the designers made the same mistake?

This seems to be a common issue w/ these amps from what I have found.  br3 and c8 blackened the pcb pretty good.  Seems easy enough to jumper that area together if the pcb is compromised.  going with the following bridge rectifier (1000V/1.5A) and recapping the amp while I'm in there.

http://www.mouser.com/Search/ProductDetail.aspx?R=W10Mvirtualkey66430000virtualkey905-W10M

 

[PRR]

> 1000V/1.5A

Hmmmm.... when a 0.9A load on a presumed 1A part *fails* in only 25 years, forcing a $50 labor charge for a 50-cent part, my inclination is to OVER-size, generously, or more.

When my furnace's two return ducts gave poor performance, I didn't go 1.5X = three ducts, I went to four ducts. And this was just poor performance, not a FAIL. When my temporary 2" board bridge fails, it's getting 6" or 8" structure.

Ah, I see. I do not know the amplifier, but I suspect they only left space for these teeny TO-5 size recyfiers. I'd struggle to get a 3A or 5A part in there. Struggle, but KNOW that I will be gone before it gives trouble again.

> 0.9A is what i was thinking too.

That's running current. Starting current is 3X to 4X higher and may continue for much of a Second, not milliSeconds like the usual silicon rectifier surge rating.

"1A" or "1.5A" is a "cool" rating. Page 2 of the datasheet for that "1.5A" part shows it is down to 0.9 Amps at just 80 deg C, which is not implausible inside an over-stuffed tube amp.

G3SBA20L-E3/51 claims 4 Amps. The package is much bigger, a struggle. However it derates to 0.9A at 100 deg C, which _is_ unlikely in a tube amp. It costs 60 cents more than the "1.5A" part you linked, but IMHO this is cheap for *never* having that trouble again.