the Poor Man 660 support thread

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Guys,

do not swap those tubes until you have solved your PSU problems! As far as I know many of you are using the original rondo or edcor transformers, and they are both way underspecified. I mean seriously, why didn't I open my mouth when you guys were arranging the edcor group buy, at least the disaster could have been partially averted. If I remember correctly those transformers were specified at exactly the total heater requirement for two channels. This is very bad! You need like twice or perhaps 1.5X of more power for safety headroom to prevent issues exactly like many of you have seen.

Those transformers will barely power up the heaters of two channels. The issue is indeed the 5687 tube and the very high 900mA requirement. If several of them decide to eat a whole 1A of current (which is entirely possible) the transformer might already be over saturated, near breaking point. Danger zone.

Get another heater transformer and you will be able to run all four of the 5687 tubes. Don't swap in any alternatives like ECC99 or 6N6P. Their heaters are something like 700-800mA and it will not help much, if at all.
 
Kingston said:
Guys,

do not swap those tubes until you have solved your PSU problems! As far as I know many of you are using the original rondo or edcor transformers, and they are both way underspecified. I mean seriously, why didn't I open my mouth when you guys were arranging the edcor group buy, at least the disaster could have been partially averted. If I remember correctly those transformers were specified at exactly the total heater requirement for two channels. This is very bad! You need like twice or perhaps 1.5X of more power for safety headroom to prevent issues exactly like many of you have seen.

Those transformers will barely power up the heaters of two channels. The issue is indeed the 5687 tube and the very high 900mA requirement. If several of them decide to eat a whole 1A of current (which is entirely possible) the transformer might already be over saturated, near breaking point. Danger zone.

Get another heater transformer and you will be able to run all four of the 5687 tubes. Don't swap in any alternatives like ECC99 or 6N6P. Their heaters are something like 700-800mA and it will not help much, if at all.
Click to expand...

So, basically, from your POV, there´s no workaround without a bigger PT ?

I have mine running with only one 5687 per channel and modified time constants. Smaller caps. Gorgeous. But as always, i´m a bit concerned about the heat...think long term.


 
skal1 said:
HI ppa

can not see the schematic you post , and i do not understand the mods  you have suggested

cheers

skal1
Click to expand...

I am re-drawing the schematic.
however, I have used the schematic of the PSU posted here, than I have added I have added some components and changed the values of others.

 
 

 
Silvas said:
So, basically, from your POV, there´s no workaround without a bigger PT ?

I have mine running with only one 5687 per channel and modified time constants. Smaller caps. Gorgeous. But as always, i´m a bit concerned about the heat...think long term.
Click to expand...

That's why I built mine in the deepest case I could find with significant ventilation. It still needs to have at least one extra 1U space on top if you install it in a rack.

There are no shortcuts. The side chain is a terrible brute force thing and there is no going around that fact.

Until someone designs a vari mu with a chip amp sidechain.
 
this the schematic of the psu modified with colors, red and azur, to indicate the components added , those with red points near them, or with values changed , those with near azur points .

IMPORTANT: ATTENTION ! to do this modifications has risks of electric shock, fire and other very dangerous damages, I am NO responsible on these my schematics I have posted here in any case! Use these schematics at your own risk!

 

Attachments

  • PM670 PSU MOD PPA 2.JPG
    PM670 PSU MOD PPA 2.JPG
    164.3 KB · Views: 405
radiance said:
So, why is it that Dingo had problems with the stock PSU and I (and lots of others) don't?
Click to expand...

this question I have asked myself many times ...
(but not only Dingo had problems, my guess is around one of ten builds, most times other IRF840s solved the problem)
 
i actually had to rebuild the 245v area once. It worked fine for the first start up and then several hours of initial testing. Next start up and puff the magic smoke. had to replace all the little mpsa´s and IRF840. It worked fine ever since and I never bothered to figure what really happened.

I´ve seen that same story here over and over again. I like the way pier pablos new plan is filled with protection diodes.

The underpowered heater PSU issue is obviously not related to this and the 136V regulator area always worked fine.
 
hello kingston
my  past problem with the high rail voltage  is the same you have i think
one channel work ok...when two channel in ...q4 ..died

have done pier paolo mod on the psu and all problem gone away ;D
all high voltage are solid with both channel and all tubes
maybe 245v is little high have 254 on tube pin ....but sounds great!!!
give a try ...is not so complicated


6.3 rail have it s own transformer
scamp booster ,relays ,and illumination have separate psu and transformer
have used sowter 4383 for input
dingo.
 
Regarding the modified PSU are you sure the 136V section works and your not missing something there?

I breadboard it and am having problems getting more than 60V out, the 245V side is reading about 10V high.
 
I completed a couple more poorman psu pcbs - all rock solid and no issues after lots of hours of usage.

I accidentally shorted out the hv - smoked a couple of resistors, but it was fine on their replacement.
No dead semiconductors at all!
 
kazper said:
Regarding the modified PSU are you sure the 136V section works and your not missing something there?

I breadboard it and am having problems getting more than 60V out, the 245V side is reading about 10V high.
Click to expand...

all mods I have suggested have a reason to be , moreover I have simulated them and Dingo has tested them, but if you did not errors, maybe there are other problems in the PSU, but I don't think it.  
 
alexc said:
I completed a couple more poorman psu pcbs - all rock solid and no issues after lots of hours of usage.

I accidentally shorted out the hv - smoked a couple of resistors, but it was fine on their replacement.
No dead semiconductors at all!
Click to expand...

just to be clear

I like the original schematic done by Analag, as I have told in my previus post.
This PSU run good and with high performances without any mod for a LOT of cases, but only in a few of cases there are  problems.
 
Kingston said:
i actually had to rebuild the 245v area once. It worked fine for the first start up and then several hours of initial testing. Next start up and puff the magic smoke. had to replace all the little mpsa´s and IRF840. It worked fine ever since and I never bothered to figure what really happened.

I´ve seen that same story here over and over again. I like the way pier pablos new plan is filled with protection diodes.

The underpowered heater PSU issue is obviously not related to this and the 136V regulator area always worked fine.
Click to expand...

the problem is C5 that, only in a few of cases, is not discharged as it should be when the PSU turned off, so it gives overvoltages and inverted voltages to other components. C5 remains charged when the other caps are discharged when the PSU turned off, this is the problem. For this case the protection diodes.
 

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