the Poor Man 660 support thread

elektrovolt

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test - wired one channel, with regular two deck pots. it works! but I have this hum that is a bit annoying. the trimpot on the heater board has no effect on the voltage, should it ?
the meter doesn't move tightly, I think because of the long swing the needle has to do - but they were cheap...

just ran some music through it, it seems to work best on acoustic stuff. sounds quite good to me, very soft, no urei 175 slamming...
 

Moby

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test - wired one channel, with regular two deck pots. it works! but I have this hum that is a bit annoying. the trimpot on the heater board has no effect on the voltage, should it ?
Hum is probably caused by mains transformer but reflected on audio transformers. Try to move around T1. I doubt that heater voltage can cause hum with 6BC8. Of course that trim have to change voltage of 3 pin regulator.
 

elektrovolt

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the hum problem is solved, I just forgot to make the ground connection on the input / output board :)

although, it is quite noisy, slightly dulling the sound and lots of  'messy' bass response, problably due to the transformers.
filament voltage is only around 5, 7 volts, can't get this higher ?!?

strange enough I cannot get the attack pot working, it seems to be working in a slow setting only.

edit: ZAP ! there we go. the trimpot between the meter connections touched ground. now there is only a low, distorted sound, and the treshold pot isn't reacting, meter neither.
I hope I didn't blow a transformer  :'( swapped the tubes, when turning on, there comes a little bit of sound, meter moves a little, then sound and meter are dropping till there's no sound at all...

measured the power supply outputs: 245 V line gives 130 V, the 136 V line gives around 70 V.
 

Moby

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filament voltage is only around 5, 7 volts, can't get this higher ?!?
Measure the voltage before regulator. If you have 6.3V unloaded and you measure big drop after loading than your transformer can't do the job. If you don't have a big drop when it's loaded try to skip (short) the 1. 0.22ohm resistor, it may help a bit to reach 6.3V  ;)
 

elektrovolt

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that is a good one, thanks.
but first I have to check this big problem I have now... maybe a new IRF840 instead of the IRF820, the power transformer is ok, and gives 270 V instead of 250 V, it is one of Bernd Bruening's.
I will ask him about this.

another thing, one of the tube sockets did not make a good contact. now I see that one copper trace on the pcb is coming off the base itself ! I know how to solder, so that is not the cause. this pcb is unusable now. anyone else ?
 

Pynta Studios

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Did anyone see this: http://dripelectronics.com/660.html?

Seems like a very cool way to get it done with good parts and much less soldering!

 

[silent:arts]

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Pynta Studios said:
Did anyone see this: http://dripelectronics.com/660.html?

Seems like a very cool way to get it done with good parts and much less soldering!

nice, like all projects from Gregory.
but where do you see "less soldering" :D

on the other side, for the price of the Sowter transformers you could pay a soldering guy to solder your PoorMan ;D
but if you don't like soldering you shouldn't DIY ;)
 

Moby

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Seems like a very cool way to get it done with good parts and much less soldering!
Doesn't make sense to do real 670 on PCB. Unless you want to make 100 pcs  ;D
 

elektrovolt

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Drip's designs are looking very good and well documented. His website says he is comping up with a Pultec EQ soon, very interesting :)
I am planning to build a 175 limiter soon.

but first I have to get rid of these problems with my poor man now...
 

e.oelberg

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Is their any downside of using a LL1540 10K/10K in the input section of the pm 660 ?

nicholas
 

elektrovolt

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I really need some help with this.
one of the meter poles touched ground. now there is no sound anymore.
the 12 and 17 volt lines are ok, but the 136 and 245 volt lines give 62 and 120.
the power transformer is ok, after the diodes there is 375 volts.

replaced the IRF 840's and the 100V zener, but still nothing.

anyone ?
 

radiance

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Probably a blown resistor...check all resistors in the first part (Q4) of the PSU...might need to unsolder some on one side to get an exact reading on the actual resistance value...
 

elektrovolt

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yes, nothing connected to the PSU.
when connecting one board it gives about the same.
I am not a real expert, but reason tells me the problem lies somewhere in the PSU board.
 

radiance

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Did you measure all resistors around Q4? Before measuring you should de-solder 1 leg and pull it out of the pcb.
Can't measure exact values when the resistors are still in the circuit.

I know this is a pita, therefore I keep a space of about 5mm between the resistor and the pcb.
Makes de-soldering a lot easier, or you can even just cut the resistors out and solder the new one on the legs of the previous one which are still attached to the PCB.

An easier way would be to measure the voltage on various stages of the PSU, to see where it drops.
This way you'll know where to start searching for a bad resistor. However, I found that it's quite hard to poke around without shorting stuff and causing even more problems. All these high voltages are not going to give me a steady hand...
 

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