the Poor Man 660 support thread

[living sounds]

Thanks! I'm using the group buy torroid, too. After the big rectifier I get around 11V DC at the input of the slow start heater PSU. Right now I'm using just one PM660 channel for testing. The heater PSU gets warm (regulator, big resistors), but not excessively. With the heater PSU connected to the PM660 channel the voltage drops to minimal amounts (ca. 0.1 V), and no amount of turning the heater trimmer can change that (unconnected I can set it to anywhere between 0 and 11V DC). The input voltage at the heater PSU remains at 11V.

Have you tried taking 2 tubes out?

No, I'll do that next, thanks!

 

[living sounds]

Tried the heater PSU with both PM660 channel boards now, as well as with 0, 1, 2, 3, 4 tubes. As soon as at least one tube is inserted, the heater voltage drops to a few hundred mV. Could there be a fault on the heater PSU boards?

 

[Kingston]

The boards are fine.

How are you cooling the regulator, since it obviously goes into a thermal protection mode? It will not last a single second powering even one poorman channel. It needs significant cooling, and bolting it to a case is not even close enough. Think CPU coolers, not the usual tiny black blocks from electronics stores.

 

[radiance]

And just in case...R1 & R4 are 0,22R  or  0R22   

 

[Kingston]

Those resistors are unnecessary by the way. There are some extreme cases where they protect from oscillation, or remove a bit of white noise from the regulator output.

But none apply when powering a bunch of simple light bulbs.

 

[living sounds]

Thanks! It works now, got rid of those 22R resistors. They came with the heater PSU kit and I didn't realize they were the wrong value...

 

[Kingston]

massive difference between 22 ohm vs. 0.22 ohm with these currents. 1.1V drop vs. 110V drop! Who ever sold you that kit should be tried and executed. I can't help but think of some pretty lethal scenarios if the voltage drop should have been the other way and there is a similar error.

 

[living sounds]

massive difference between 22 ohm vs. 0.22 ohm with these currents. 1.1V drop vs. 110V drop! Who ever sold you that kit should be tried and executed. I can't help but think of some pretty lethal scenarios if the voltage drop should have been the other way and there is a similar error.

It was someone from this board (I could look it up, but why bother), I guess he bought the parts and never build the PM670, and didn't realize his error. I should have taken a closer look at the PCB.

 

[dingo]

hello !
have some problem with my psu

the main problem is on irf840 Q4
with  psu connected to both audio pcb no tubes, all wiring done
all the voltage are ok ,
have two multimeter here one measuring 245-133-6.3-+17-17
the second one (amperometer clamp-and voltmeter) measuring all the voltage with 15v difference on 245 rail have 259 ,135rail about143
and so on! don t know which one choose as reference ? if do a media  i think i am little up with voltage!!! or it is ok?

when put all tubes on one channel only ,fire up ....voltage are ok tested for about 1-2 hours sound great !!!
no distortion,hum, noise. stock time constant  sounds good ,scamp booster sounds great .

have two little fan on slow start heater  and on q4 big heat sink  so temperature are not high
slow start is about 2,4 A

the problem is when turn off  the machine and after long discharge
turn on again ....and Q4 voltage drop down to 40 v!!! ???
replaced q4 start up ...all ok  ...turn off ..discharge...turn on.... same problem as before!!!!
have replaced C6 with 0,47uf 400v,
have  one ntc on the primary transformer but no difference!
any ideas!!
thanks!

 

[radiance]

the problem is when turn off  the machine and after long discharge
turn on again ....and Q4 voltage drop down to 40 v!!! ???
replaced q4 start up ...all ok  ...turn off ..discharge...turn on.... same problem as before!!!!
have replaced C6 with 0,47uf 400v,
have   one ntc on the primary transformer but no difference!
any ideas!!
thanks!

It must be something with the components surrounding Q4...
How many times have you de-soldered Q4 already? I've heard from other people that this PSU board is not very forgiving when it comes to de-soldering and such...
I know it sucks, but you'll have to re-check all resistor values and make sure they're all ok...same for diodes and transistors and caps.
Look for solder mistakes & shorts...it might be a tiny drop of solder or so...
Also, maybe post a picture of your setup..so we can see your heat sinks and all...

 

[dingo]

radiance!
q4  and the 3 small mpsa are on socket so don t need desolder
at the moment have changed D8  and tested with no tube  and all voltage are ok
the strange is every things seem to be ok  at firt start up with tubes ...and sound good
there are no shorts and bad solder checked wery well all points all r values are ok
will post some pics!

 

[dingo]

here some pics

 

 

 

 

 

[radiance]

radiance!
q4  and the 3 small mpsa are on socket so don t need desolder
at the moment have changed D8  and tested with no tube  and all voltage are ok
the strange is every things seem to be ok  at firt start up with tubes ...and sound good
there are no shorts and bad solder checked wery well all points all r values are ok
will post some pics!

I'm kinda clueless here...maybe it has to do with the toroid which is underpowered IMHO..but than again, it seems that other people are using this toroid without any troubles.

 

[dingo]

radiance!
think have solved the problem
have replaced both q4 and q5 with fresh irf840b
replaced d8 and the 3 small mpsa,replaced c2 c3 just because have some spare
have wired 3ntc,s 10 ohm in series to primary  trsf
and now have one channel working !! 
have tried different shut down and start up  and al voltage are there and stable
maybe 245 rail is little up ...got 250 on psu side  ...and 245 on tube pin ...or it is ok!!?!!
will try with both channel soon!! and see if voltages drop down again
thanks!!

 

[dingo]

no way!!!! ???
have wired both channel ...voltage stay at 245 for about1 minute..then drop to 220....afetr 2 min  drop to 40v
have to replace again irf840.. hope not mpsa!!
have some irf B11N50A can use those in place of irf840??
am thinking about a new and better  psu!!!! any idea?
any other ideas from other  pm???

 

[skal1]

dingo have you implemented to mod analogy suggested ?  then read this may help  http://www.groupdiy.com/index.php?topic=28274.2560

skal1 

 

[dingo]

hello! skal1
yes have read several time all the problem about the psu 
have just changed c6 with 0.47uf 400v
now the main problem is that psu can not handle two channel
one channel all tube it is ok
two channel all 6bc8  two 5687 no go!!
the high voltage rail fail
my trasformer is rondo from silent-arts
one channel slow start heater draw about 2,4 All tube  ...it is ok..two channel would be about 4,8
so i am in the range of max 6a

more powerfull psu maybe?

 

[living sounds]

I've wired up one channel but all I get is an attenuated, distorted signal. I've looked at it with the scope, and the signal going to the second transformer is already distorted. Any idea what to look for? The 6BC8 also get a lot hotter than the 5687...

 

[radiance]

more powerfull psu maybe?

I've an extra 8A toroid just for the second heater. To me it seems the toroid from silent-arts is underpowered but like I said before, other people have no problems with this toroid.

 

[radiance]

I've wired up one channel but all I get is an attenuated, distorted signal. I've looked at it with the scope, and the signal going to the second transformer is already distorted. Any idea what to look for? The 6BC8 also get a lot hotter than the 5687...

What level signal? Did you match your tubes?