Jordan Two/04 schematic needed

[tim]

I picked up this amp from one of my drop off music stores yesterday. It's a
70's solidstate amp and very ugly. Anyway, before I get into this thing at all, it would be nice to have a schematic in my hands. I could purchase one but if someone has one they could copy and email me, it would save my customer $20.
Thanks.

tvendt (a/t) comcast (d/ot) net

[Enzo]

$20 aside, what are they willing to spend on it in the first place?

I'm not familiar with the brand.

[tim]

Good question...I charge $20 just to look at it...usually I charge an hour before I call them....I am going to put it on the bench tomorrow and check it out. I haven't even powered it up yet....You can bet I'll plug it into my limiting lamps first.

[Enzo]

Is the fuse blown? I'd measure for shorted outputs before I applied power, limiter lamps or no limiter lamps. SHorted recto and filter cap check first too.

[tim]

Hi Enzo...nope, fuse Ok. Once I figured out how to get the amp out of the cabinet (hidden screws under handle end caps), I was able to determine that the +9 volts was missing (at least) and that's about as far as I got before my 1/2 hour bench time was up. I could tell it was going to go well over an hour trying to trace the voltage around and find out what was dragging it down. It went back and forth across several boards. I can fix almost anything with tubes without a schematic and alot of solidstate stuff too without one as long as I have a bit of experience on it but this is like they sprinkles the parts on it haphazardly and just ran traces to where ever they fell. A schematic is essential on this one...so the store I picked it up at calls their customer who owns it and he wants me to tell him what the bad parts are so he can get them and install them himself....I said...ummmmmmmmmmmmm; no! Well, no loss, I make $20 and he gets his amp back not working. I get nervous working on that old solid state stuff, trying to cross transistors, twisting legs around to fit different EBC footprints than it was originally laid out for.....I quoted him 2-3 hours. He thought that was way too long. Oh well.
Tim

[Enzo]

You shouldn't have to do the leg dance. For example the typical Jap xstr TO92 is ECB, while the USA one is EBC. In an emergancy you can replace one with the other and do the leg thing, but so many perfectly fine subs exist within both leg arrangements it is not needed. Most of the other packages are universal. There are a few reverse TO126s, but they are specific. A few well selected types in the US, Jap, and BC series xstrs will cover most situations. Unlike tubes, transistors are REMARKABLY versatile and flexible in substitutions.

[tim]

Enzo,
Thanks for the insight. In my shop, about 75% of what I do is tube stuff (or hybrid). Most of the solid state stuff I do is newer stuff where direct replacement parts are generally available. Up until 3 weeks ago, I was repairing stuff as a part time "hobby" business but have decided to pursue it full time. I guess I'll be seeing more older s/s stuff in like the Jordan. You mentioned "a few well selected parts".....if you were going to have these in your shop (and I assume you do), what would you order that would cover most of the repairs you do? I have quite a few transistors (small signal) here but never seem to have the right one so I have to do the cross reference thing and the "leg dance" routine. I'm putting together an order of other stuff and could flesh it out with needed transistors to meet the minimums.
Thanks for your help....
Tim

[Enzo]

Oh geez, I'd have to ponder. When I buy xstrs, I usually get 5 if I need one. SOme common types I buy a lot of.

The thing is that small signal transistors are mostly interchangable. Meet the voltage and current needs and if it is a darlington or not - rare in preamps - and pretty much all of them work fine. It is not like 12AX7 versus 12AT7 versus 6AN8 or something. 6SL7 and 6SC7 are more or less teh same thing except one has a common cathode - so they are not interchangable. But the transistors are not like that.

SOme are lower noise than others, adn that matters in the front end sometimes, especially in like a mic input stage on a mic board, but in a power amp noise is rarely an issue

In American type TO92 NPN, let's say 30v and 100ma or higher rating, the following are essentially interchangable:

2N4123, MPS2222, MPS6531, MPSA20, 2N4401, 2N3904 from the general purpose list
Add 2N5088, MPS8097, 2N5210 from the low noise list
And higher volatge parts MPSA42 (MPSA92 PNP)

There are plenty others, those are just from a quick look through the Motorola book. I suspect ON Semiconductor - what Moto is these days - has a product selector guide, check their site. I think I have all of those in stock, and many more. I have a wall of parts. But really, MPS8097 and 2N4401 would probably do for me. SOmething similar for PNP of course. I also have a ton of MPSA06 - 80v, 500ma general purpose. Will act as an amp, will drive a littel relay, whatever, and cheap. A lot of these are like 6 cents in 100 lot. Check Jameco, their catalog page has a listing of general types.

MCM carries foreign number parts at reasonable prices. Maybe cheaper elsewhere, maybe not. There is a selector guide in the seniconductor section of their catalog. Page 365 in catalog 50. SYggests typical general purpose selections by body type

From that, TO92 NPN:
2SC945 - the ultimate use it anywhere little part
2SC1815 - I reach for this one first.

2SA733, 2SA1015 - PNP

And higher vootage like 2SC2240, but really, HV parts are only foudn in power amps, so when you encounter one, order the same type and get a couple extras.

TO220, I have a few. Seems QSC used a certain pair as drivers a lot, (I think SWR too if I recall) so I srocked up on them, And I use them most everywhere else as drivers. Lo and behold, there they are on the MCM suggestion list:
2SC3298 and 2SA1306 - 160v 1.5A. Since the TO220s are all the same pinout, These work as well as US types.

I do have a lot of other types too, and I might reach for MJE15030 (MJE15031 PNP) 150v 8A. Heftier than the above Jap types.

SUbs are very easy. VOltage can be anything at or over your target. I try to keep current ratings at least similar. DOn't stick a 20A part where a 3A part goes, but 5 or 6? Sure.

In high power stuff don't mix outputs - in fact anything in parallel with another wants to be the same as each other. SO if my old QSC power amp has a row of 2SB555 outputs, I can replace the row of them with MJ15025, but don't mix. All of one or all of another. I think the counterfeit problem is greater in Jap number parts, but it is only a matter of time until they cover US parts, so buy from a good supplier. I buy my Moto parts from Allied, and MC has been good on Jap stuff.

On TO3, I look at MJ15024 NPN and 15025 PNP as more or less universal high power replacements. Thoug I will be more selective since I stock many types. If MJ15003 is nore appropriate, I use it. They will be phasing them out, so the MJ21193/21194 pair will be my choice in the future.

But I fix a lot of PV, and they use the Moto parts. If you wind up doing a lot of Yamaha, you won't see the TO3s at all.

I built up my parts a little at a time. It is hard to think about a kit for starting from zero.

SS is not hard to work on for me. And that's not bragging, they are all similar just like 50 watt push pull tube amps are really all pretty much alike. I bet you coul;d draw a complete amp schem,atic on a napkin in a bar and not miss much. Might not match a specific model anywhere, but would be a reasonable circuit. SS is like that, once you recognize the circuit, they are all pretty similar.

If you do general repairs, there are a few chip amps that come up. The TDA2040/2050 is a five leg RO220 amp chip found in soooooo many little practice amps. The larger amps are using TDA7293V - MArshall and others - and the LM3886.

Many parts are common in the industry, so I often have the exact part, but when I don't, I usually have something close enough for a sub, and it really is OK to sub parts.

But really, I'd wait until I need something and start a list. If you service PV you wont see many 2SC/2SA numbers. and if you service Samson, you will.

[Krong]

Thanks for the info Enzo. This will help me imeasurably.