Identification of unknown PA amplifier

[Luxman1050]

I'll give you some good photos of the board. At some stage I'll map the circuit out as you know can be a bit time consuming.
Well lucky enough I've just found these transistors exact match and only 2 left of each so be buying those now.

[Herald1360]

Originally Posted by Herald1360

TIP30(C), TIP34(C) are common Texas parts. 8223 is date code, week 23 1983. The C suffix relates to voltage rating of 100V.

Oops- that should be week23, 1982!

[Luxman1050]

I got the code wrong on one they are TIP33C & TIP34C Not sure why 30 was in my head.
Well lucky enough I've managed to source NOS for both and also the little chips think that's what they are. Could not source the power transistors plenty of so called new around but I'd think there copies and bound to be completely different spec to the originals. Could take a chance but have a think on that one.

[Trevor]

What is the little 8 pin chip ref no
I have been busy all day working on a minimalist amplifier schematic because of the one you have posted 50 watts plus out of 1 op amp and 4 transistors
trev

[Luxman1050]

Your getting quite into that Trev.
Texas 741(uA741CP)

[Trevor]

Yep
I thought it would be a 741 back in the day this was the goto op-amp
H+H used them a lot as well as other manufacturers
Same as in the Texan also !
I have drawn three variants on this them today
Not been so keen in a long long time
Many thanks
Trev

[Luxman1050]

I also managed to get nos bridge rectifiers for it as well. So when all come and fitted it should run like new.
Glad it's spurred up an interest for you again.

[Luxman1050]

Well your not gonna get these as genuine parts.
2SB554/2SD424 none have that figure of 8 recess on their bases all flat bumer.

[Trevor]

Plenty of equivalents out there but beware of the fakes.
Trev

[Luxman1050]

Okay Trev any suggestions most welcome.
So are you gonna build these modules? I'll pull boards out today give you resistor ratings etc. Quite a few 1/4 watt in there. I might change these all out ive used AMRG resistors before come in 0.75w and 2 watt bit expensive but reliability and sound reproduction perfect. I've used many resistors from 5p upwards obviouslyif you have a 1930s valve radio your not gonna chuck in quality resistors no point. But if you have a quality bit of kit worth the investment. This amp cost me nothing up until now and I already had some large panasonic psu caps so I'd quite happily spend around 100 quid on it. Oh had to buy XLR connectors I have plenty of rca panel mount sockets but wanted to keep the xlr sockets.
Keep going Trev be interesting to see what you come up with.

[Trevor]

The first transistors that come to mind are mj15024/mj15025
These are used by lots of high power amplifier manufactures are available at a fair price and are well known to be robust
Obtain from a trusted source I use Rs /Farnell

Trev

[Luxman1050]

Okay cheers Trev yeah I use those never had a fake yet.
Resistors All on a single board so you would need double the amount.

Following 1/4 watt 5%
10k x1
12k x1
22k x1
220k x1
27k x1
2.7k x4
3.3r x2
1.5k x1
10r x1
330r x1
33k x1
4.7k x1

680r 10%

3.4k x2 1 watt

40r x1 2%

27k x2 wirewound 5 watt?
72r x1 wirewound 5 watt? Might both be 7 watt.

22k carbon track preset potentiometer marked E

Main electrolytics where 2500uf dual cans 63v x4

The other 2 are 22uf 63v.

Hopefully that's of some help.

[Luxman1050]

Looking at those I would assume I'd need the bipolar not the npn?
Cheers Chris

[Radio Wrangler]

Originally Posted by cdm1christopher

Looking at those I would assume I'd need the bipolar not the npn?
Cheers Chris

?

Something got lost in translation... NPN and PNP are both bipolar transistors, just opposite polarity types.

David

[Luxman1050]

Got it now 2sb554 is a pnp
2sd424 is npn

[Trevor]

The 27k x 2 are you sure I suspect 270 ohm x 2
Trev

[Luxman1050]

The green one pic attached read it wrong saw 27k moved round R27K
But I'm getting 0.5r reading?

[Luxman1050]

Are you meaning the wirewound or the 1/4 watt?
Pic of two 1/4 red violet orange 27k.

[Luxman1050]

Looking at my ones the pf collector capacitance rating on mj,s is only 500 whereas on originals 700pf and 900pf so thats 30%/45% difference. Should that be okay?

[Luxman1050]

I'll pull those wirewound out numbers on case not tallying with readings I'm getting one is reading 0.3r but has r27k and other 72r but reading 33r? Could be because in circuit.