the Poor Man 660 support thread

[G-Sun]

I posted a lot of pictures here to give also less experienced builders an impression what it could look like and to learn from.

Fantastic build bernbrue. Thanks for sharing!

 

[Hasse]

Can anyone help me by measuring your reading across the R17?
I've just finished my "pm670" and one channel has a looong release. I found that the reading across that resistor measure 221k but the other channels resistor (r17) measure 9k. Both resistors are 221k. Which is right?
I've changed the diodes, checked all resistors in the time constant network and checked the transformer. Everything seem to be allright but something must be wrong...
It works fine in Stereo mode but not in mono. Seems like there must be something wrong with that network.

 

[Hasse]

Solved!
The diodes on the card whith the short release was PH4148. Zener... Right diode is 1N4148.

 

[mdainsd]

Just wading into this thing. I purchased a non-working 660 from forum member "matta". He had been working on it on again off again since 2008, with no joy. Matta did a real nice build with great workmanship.

Where in this 157 page thread are the most up to date schematics?

First thing to do will be build a working power supply. I'd like to find information on the complete power supply board to see if it can be salvaged moving forward. Or just do a new HT board with a -12.6V section ala Kingston.

Having read this thread a couple of times through, it seems the Achilles heels of these are the power supply and the abysmal quality of the Edcor transformers. One poster saying that he had 6 bad out of 8? Incredible.

 

[duantro]

Hello Mdainsd,
I agree the edcor input trannies were fairly grainy. I've done the cinemag inputs and used Kingston's m670 mods ( except haven't done his power supply yet). I am using moby's regulated 6v boards and the few mods to the existing psu from analag, and a 11amp 6v tranny!. I can look at my notes later if you'd like. If I were you I'd go straight to the m670 mod. Mine sounds fantastic with the partial mods that I've done.

 

[mdainsd]

Yes, I would be most interested in what you have.

I am definitely thinking about the m670 mods, but first things first, the power supply...

Thanks!

 

[duantro]

For the PSU I have changed c1 and c3 to 450V, Q4 to IRF840, C6 to a panasonic film cap 47uf/400V. I think that was it, besides using an 11amp (overkill) heater tranny and Moby's regulated heater boards- which IIRC Matta had addressed these issues already.
I also installed a thermister controlled fan after the regulator got so hot it melted a wire after about an 8 hour session!

 

[mdainsd]

Did you do the cap mod to the two output transformers? Yes, my unit has the heater boards in it. The first thing is spec'ing a new PT. The one in it only has 220V primary windings. Im hunting around for an appropriate substitute. Ideally I will find a 0-240-260-280V secondary with a single 15V, 5 (or so)A winding.

 

[duantro]

What is the output cap mod that you are referring to? I have done most of the Kingston m670 mods. Let me know if you find a power transformer at these specs. I'd like to do the Kingston power supply also.

 

[mdainsd]

this thread is where the cap comes up. They are in the schematic in post #1

http://groupdiy.com/index.php?topic=51478.0

 

[duantro]

Yes I have done this m670 mod. It works great! Wasn't sure if you were talking about the pm670 or m670 at first.

 

[Freddy G]

My poorman 670 is working and it sounds fantastic! I need a little help on the gain and threshold switches. I got the 2 pole Uraltone switches but for the life of me I can't figure out how to load them and what value of resistors. Yes, I've seen the calculators and such but I just can't wrap my head around that. If some kind soul could just draw it out for me with values I would so appreciate it. right now I'm just using 20k dual pots. Please! Help!

I feel so stupid....I built the whole thing with no problems and this last thing is just killing me!

The switches I have are like these:

 

[duantro]

It's laid out pretty good in the meta... http://groupdiy.com/index.php?topic=28274.msg413222#msg413222

 

[Freddy G]

Thanks.
Yes I know about that chart. Which is why I feel so stupid! I need it laid out for me a little more like paint by numbers :-[

For that matter I can't understand how this switch would even work. Since I'm using a dual pot wouldn't I need a 4 pole switch?

 

[duantro]

if it is still confusing, check page 100 starting at post 1997.
Keep in mind there are errors on post 1993.
I've swittched to 600r T-pads on the input gain when I did Kingstons m670 mods and switched to non center tapped cinemags.

 

[Freddy G]

Yes I'm still confused.

Let me just refer to one line of Kingston's chart. 

Step 1, Attenuation = 22 dB, Rx = 13809 ohms, Ry = 1191 ohms, Resistor = 1191 ohms.

Am I to understand then that for just this one step there are 3 resistors?

 

[mitsos]

I think the actual resistor value for each step is the last value in each line.  Kingston says the total R is 15K.  It's like a pot/ voltage divider like a volume pot.  Signal goes in on top and out the wiper, other side (in the volume pot example) goes to ground, but here the two "pots" connect together and is where the control voltage goes. 

Anyway, between the CCW position 1 and position 2, is where the 1191R resistor goes.  Between pin 2 and 3 should be a 309R, pins 3 and 4 a 183R, and so on til you get to the end of the each section. Signal would go from the trafo to last pin (CW) of the respective switch sections, the first positions (CCW) would connect together and go to CV and the poles of each switch go to the grids of the valves. 

 

[Freddy G]

Thanks fellas!

Now I get it.

 

[weiss]

Anyone got a power trafo left? searching one for my pm 670..
btw: is it problematic to use 25k stepped pots for gain & threshold?

thanks
weiss

 

[duantro]

http://www.diyaudio.com/wiki/TransformerSuppliers
Be aware that some have stated problems with the spec'd power transformers and recommended getting one with a higher current rated heater line. I currently have the Rondo (15v /250 v) and a Triad 9v/ 11a monster for heaters and don't have any issues.