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The Acoustic Club

#5,621
StingRay85 said:
I bought it in Germany from a home clean-out. Apperently there was still a bill of 400 usd with the amp, therefore I expect the condition is good. I have a 120-240V converter of 60W that I can use to see if it fires up and plays. Considering to use the transformer of my donor 220 if it matches the power.
Click to expand...

OK, I just took a look at a 370 I had, domestic USA version with the 4-wire power transformer. Its transformer is stamped with a 56-8A part number (a.k.a. 560008A). The 270 & 370 service manuals list the part number as 560014. I deduce from this that the '08A is the domestic 4-wire transformer and the '014 is the export 6-wire transformer. It's possible they eventually used the 560014 in domestic models too, I just don't have time now to open all mine up to see if I can find one.

The good news is that the 220 apparently used the same 560014 6-wire transformer, so it would be an easy swap between amps if you end up needing it.
 
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#5,623
JacklegBass said:
OK, I just took a look at a 370 I had, domestic USA version with the 4-wire power transformer. Its transformer is stamped with a 56-8A part number (a.k.a. 560008A). The 270 & 370 service manuals list the part number as 560014. I deduce from this that the '08A is the domestic 4-wire transformer and the '014 is the export 6-wire transformer. It's possible they eventually used the 560014 in domestic models too, I just don't have time now to open all mine up to see if I can find one.

The good news is that the 220 apparently used the same 560014 6-wire transformer, so it would be an easy swap between amps if you end up needing it.
Click to expand...

Awesome, thanks for the info
 
#5,627
B46CFA4D-DEA1-42F3-BBE5-BF40FF6F9F44.jpeg
BF864A14-FD19-4D81-A572-2B2D577F31C9.jpeg
EB0C3DF6-29D9-4C25-9C51-BE6888F647BF.jpeg
Both sides of the fence sound good
 
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#5,628
StingRay85 said:
Sounds like a ground loop
Click to expand...
It's not a ground loop, it's not a 60 cycle hum, the outlet due to being cheap becomes a diode and the old amps plugged into don't like it and are fuzzy as all get out. When I plugged into another room, both Acoustics sounded stellar, no fuzz or cutting out. Like I said, the old man did a number on the simple things around here
 
#5,632
JacklegBass said:
OK, I just took a look at a 370 I had, domestic USA version with the 4-wire power transformer. Its transformer is stamped with a 56-8A part number (a.k.a. 560008A). The 270 & 370 service manuals list the part number as 560014. I deduce from this that the '08A is the domestic 4-wire transformer and the '014 is the export 6-wire transformer. It's possible they eventually used the 560014 in domestic models too, I just don't have time now to open all mine up to see if I can find one.

The good news is that the 220 apparently used the same 560014 6-wire transformer, so it would be an easy swap between amps if you end up needing it.
Click to expand...

Opened in up and surely its 4 wires. Its serial number GA 1080, so probably a very early model. Also opened my other 270 and a 220, and the size of the transformer is the same. But I guess it will not be an easy swap, because there seems a bit more to it than just connecting additional two wires.

Keeping it original due to its low serial number and excellent shape might be the best idea
 
#5,634
StingRay85 said:
But I guess it will not be an easy swap, because there seems a bit more to it than just connecting additional two wires.

Keeping it original due to its low serial number and excellent shape might be the best idea
Click to expand...


Swapping-in the 6-wire 540014 transformer only involves joining together the two primary center-tap wires (white & black/white) and also re-routing one of the two wires feeding the neon indicator so one terminal of the indicator is fed from the junction of those two center tap wires instead of from the 240V input (even in 240V models the indicator runs at 120V). You could twist all three wires together in a wire nut or even better use an available terminal strip lug to solder them together. The 6-wire transformer's black & red wires would go to the same places as before -- you don't have to worry about polarity.

That said, I'm always for keeping things original any time possible, so if you're happy with an external transformer/converter then that would be my preference too.
 
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#5,635
Thanks for the clarification, now I understand the reasoning behind the wiring diagram, and why PL401 is connected that way. I gotten some advice from another forum and already decided to make the swap as it is less complicated than I initially thought. I already have an external transformer for my 360, and I think it creates additional hum in some occasions. In my other 270 it looks a bit different inside, but there are indeed a couple of wires packed together and covered by white tape.

I also got the advice to remove the death cap, found via Google that you did the same with your 270
 
#5,639
StingRay85 said:
It does appear that the EQ of the 220 would fit the 450.
Click to expand...

Ouch, that's a little rough. The EQ boards in the 450 and 220 wouldn't be a straight swap. For one thing they operate with considerably different supply voltages (450=34V and 220=72V). I can't tell if the slide potentiometers in the 450 are soldered directly to the board like in a 270 or 370. but even if they were the 220 EQ board almost certainly wouldn't be drilled and etched for the slide pot leads. One good thing to keep in mind though is that both the 450 and 220 use the same five 50K slide pots (Acoustic house number 475039).

I don't know if you've already researched it and identified the inductor values, but from what I see in the picture your 450 has one original 1.5H inductor still hanging on in the rightmost position plus some kind of replacement inductor in place of the original 375mH part in the 2nd from the left position.

As oriented in your picture, going left to right you should have:

375mH* - 375mH - 750mH* - 1.5H* - 1.5H (house numbers 004* - 004 - 005* - 002* - 002).

*missing

If the substitute part is good, the board needs another 1.5H, another 375mH, and a 750mH. If the leads on those three loose inductors are broken off to the point where they can't be soldered back in place, then you could steal a good 375 and 750 from the 220's EQ board and a 1.5 from the 220's preamp board. While you're at it, if you wanted to replace the substitute part (I certainly would) you could also steal a 375 from the 220 preamp board.

FYI, it's a good idea to dab some hot glue between the base of the inductors and the PC board to keep them secure from vibration and breaking one of the leads or a solder joint.
 
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#5,640
I already checked out the 220 and indeed it's only the exterior that looks similar. I remember reading something on the inductors on the unofficial ACC board. I already had the idea that only replacing the inductors should suffice.

I can't see any obvious wires still sticking out, so no idea if this happened by vibration or just the previous owner not capable of fixing the thing

15654504798357542243655889252843.jpg 15654506500278276125941830286163.jpg

I once again appreciate your help Les
 
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