the Poor Man 660 support thread

Shop deals on ebay
shop deals on amazon
Advertise with us
GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Hello.

So, i got tired with my mains variatons problem, and i tossed in a dual LM350K-based dual regulator for the heaters....one 350K for each channel, and a big heatsink.

It's working wonders. I'm doing a long mix this days and i'm using the PM on some stuff as i type this. So far so good, stable. My needle zeros are more stable now (no need to recalibrate many times a day).

I'm still running on a single 5687 per channel. I tried 2 per channel with the new heaters PSU with no luck...it seems that i have some of the problematic 5687 ones, with both 5687's per channel, i get strange interaction and behavior of the controls, between channels. Seems like the high voltages are deviating with all tubes on. With only one tube, it's working nice. Time to order new 5687's and still looking for 6n5p's to try out.

The beast is hot. when the AC is turned off, the trafo gets quite hot, and so do the top of the case. i'm putting another fan to pull out hot air off the case. And my trafo is outside the case, both for heat and noise.

I''ve found this beast quite nice for strings (but only on a mix) but no luck with faster, percussive sounds. Too much distortion even with small amounts of GR. But i'm using unmatched 6bc8 tubes.

Next mod : new timing network, as kilmister describes. I want faster time constants.




 
I have good voltage readings from the PSU (not connected to anything).
I'm just about finished wiring the whole thing up. Any last minute advice before I power this monster up?

[size=10pt][size=10pt]EDIT[/size][/size]

Fired it up and it sounds awesome! Now to fool around with it for a while. Thank you Rowan and Volker!
;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D
 
I can't seem to dial in -17V with RV2. All I can do is between -18.23 and -19.4V.  And that's turning the trimmer all the way from one end to the other (where it starts clicking) Any idea what could be the trouble?
 
thanks guys, I'll check and swap those components.....but,
now I see that the 136v rail is sitting at 249V! I tried to disconnect the PSU board to see if anything changed but no, it's up at 249V
The compressor still works though, and it sounds OK
 
after pulling out chunks of hair, I finally found the problem with the -17 volt rail....broken PCB trace under the mask! I think I got a Monday morning or friday afternoon PC board because some of the traces look pretty funky...instead of nice clean lines they look like jagged torn paper.
 
Silvas said:
Hello.

So, i got tired with my mains variatons problem, and i tossed in a dual LM350K-based dual regulator for the heaters....one 350K for each channel, and a big heatsink.

It's working wonders. I'm doing a long mix this days and i'm using the PM on some stuff as i type this. So far so good, stable. My needle zeros are more stable now (no need to recalibrate many times a day).

I'm still running on a single 5687 per channel. I tried 2 per channel with the new heaters PSU with no luck...it seems that i have some of the problematic 5687 ones, with both 5687's per channel, i get strange interaction and behavior of the controls, between channels. Seems like the high voltages are deviating with all tubes on. With only one tube, it's working nice. Time to order new 5687's and still looking for 6n5p's to try out.

The beast is hot. when the AC is turned off, the trafo gets quite hot, and so do the top of the case. i'm putting another fan to pull out hot air off the case. And my trafo is outside the case, both for heat and noise.

I''ve found this beast quite nice for strings (but only on a mix) but no luck with faster, percussive sounds. Too much distortion even with small amounts of GR. But i'm using unmatched 6bc8 tubes.

Next mod : new timing network, as kilmister describes. I want faster time constants.
Click to expand...


EDIT :  The excess heat was cured with a thicker mains cable....seems that the one i was using wasn't enough. The beast is cooler now.

 
Allright, I've finally managed to build my pm670s, but unfortunately I'm having some troubles: Fired one channel up and all was fine, moved the tubes to the second channel and suddenly both high voltage rails broke down. Moved the tubes back to channel one and the problem stays - when powering the unit both high voltage rails rise up to about 2/3 of their desired values (ie. 245V goes up to ~190V) and then slowly decreases again. If I remove the tubes alltogether all psu voltages are perfectly fine?

Any ideas where I should look a bit closer? I've double and triple checked all connections, transformers and the wiring of the switches with no luck. Even with just one tube inserted both hv rails drop dead.

Thanks!
Christoph
 
After a couple of another wiring checks I've narrowed the problem down to just the 254V rail. When I unplug that from the audio boards my 136V rail stays where it should be. The weird thing though is, that whenever I just insert one 6bc8 in the board both high voltage rails stop at about 2/3 at their desired voltage, but stay there as supposed to drop (which is what's happening as described in my previous post when there are all tubes in the board)

This is a tough one, since the psu seems perfectly fine without tubes and I can't find any wiring or circuit errors.

thanks in advance,
Christoph
 
OK. Yesterday, i had some free time in the studio so i wanted to go a bit deep on the 5687 problems i´ve had with all four tubes in. After i put the dual regulated LM350K power supply, i wanted to put all tubes back (at first, i thought that my problem was underheated tubes). Then, i adjusted heaters voltage to 6.3v with all tubes in. No luck. The PM is still behaving weird with the 4 tubes. Weird ? i mean, interaction and VU dancing when moving controls.

Sorry for my english, i´ll try to explain what i did as clearly as possible, maybe this can help anyone with similar problems :

So, i read somewhere in this topic, to adjust a bit the 136v supply to make it more stable....no luck. I raised the 136 rail a bit (it was a couple volts low) with no luck. I lowered the voltage with no luck....so, probably, my problem isn´t related to the 136v PSU and/or the 6BC8´s. Now what ? as i haven´t any more 5687 tubes to test, i decided to measure the 5687 plate voltages, in both halves of T4 transformer, with 2 tubes on, and 4 tubes on, and when 4 tubes on, i measured both when the VU reacted to any change in the controls, and when the VU is stable and in 0VU. 

Now, with only 2 5687 tubes on (the way my PM it´s working quite nice), i have 245 volts on the center tap of the transformer, and the same voltage on both taps.

With 4 5687 tubes on,  and the VU somewhat stable, i have 245 volts on the center tap, and the other taps are measuring something like 245-230. Fiddling with the controls, i found a position where the VU´s are dancing around -12 or so, then i measured again and again.  inverting taps on T4 give me somewhat different voltage readings, as well as greater variations, but one thing remains common. It is always one of the two taps feeding the plates, which is showing a big voltage unbalance from 245v. The other tap is always close th 245v.

So i think i must have extremely mismatched 5687 tubes, right ? Since i got my PM working with only 2 5687 tubes, i suspected from these tubes. I´ll have to wait some time to get more (and hopefully matched) 5687´s and try again. And i´m still very happy with my comp. Right now, i´m working on a "sidechain protoboard" idea i´m veroboarding.

The idea is to have easy access to different RC combinations, and the idea is that i can easily change resistors and caps, as in a protoboard. I´ll post some pics when it´s done, installed and working.


BTW, i think my power cabling on the PM is under-rated. Im redoing this, too.

Best regards.

 
look for my posts in this thread for what I think is going on with the two vs four tubes.  

Look for Kevin's, Emrr and my posts in pages 79 to 84

As I posted before the answer for the 2 vs 4 tube issue should be easy to understand if the different tubes are curve traced and the individual heater currents are measured.  I don't think the tubes are "bad" I think the the tubes that work as a pair vs two pairs gms are X2 of what the PM was designed with and maybe the tubes are marked with the "lesser" spec tube number.

Someone should use a P3 Kill A Watt or better power meter to measure the current and power and phase angle from the wall outlet to the PM.
 
I´ve read the entire thread a couple times just to absorb all i can about this very nice piece of hardware...but between the studio and my 2-year old daugther, i can´t remember everything. I was well aware of Kevin´s `problems with his 5687´s long before i started mounting and connecting everything on my PM. That´s why i took out half of the 5687´s in the first place, and voila !

The tubes, i don´t think they are bad tubes (i tested the 5 i have, and all work OK with only 1 tube installed) . My tubes are JAN phillips, but date codes from march 1987...i just think they don´t work as two pairs. Anyway, it´s done for now, and next week i´m putting in the sidechain proto board so i´ll report later ! I´m getting new tubes, but not now.

Thanks Gus, i´ve forgotten quite a lot of what´s written on this topic.

 

Latest posts

Back
Top