the Poor Man 660 support thread

khstudio said:

Also, where are you measuring your PL1 voltages and what does your "Threshold Position 2 (or so)" actually mean?

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It means = the 1st step ON.

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So are you using a 24-position switch? 

Also, I guess you didn't see the other part of my question (I boldfaced it).

Cheers,
--
Don

fixed my post... look back.

So are you using a 24-position switch?  

Click to expand...

21 for GAIN
12 for Threshold... this shouldn't make much difference if your "Taper" is 15k LOG.
Off should be OFF
Middle should be close & FULL ON should be the same for the test procedure I gave.

My unit has one of the toroid transformers from the group buy, the line voltage was set to 118 on my variac, and I warmed it up for 30 minutes before measuring:

Power Supply

R1 - 343/339
R8 - 249/244

I used the 24-position Elma switches and the log taper from the xls file.  When making the measurements with the signal applied (1.2 volt sine wave with 1.2 volts at the output, threshold all the way off), my meters tracked the reduction nicely as I turned up the threshold.

Stereo unit, so we have:

Control Voltages

Left
Off: -4.59
Med: -6.45
Full: -8.90

Right
Off: -6.58
Med: -7.35
Full: -9.65

With no signal applied, gain and threshold off:

Left
R1: -1.836/-0.807
R10: 12.26/0
R11: 12.42/12.90

Right
R1: -1.862/-1.292
R10: 13.96/0
R11: 13.98/12.54

Hope this helps.

Cheers,
--
Don

GREAT... one more voltage reading.  ;D
Keep them coming!

Also, If anyone thinks there should be MORE TEST POINT'S... Please posts them

khstudio said:

...
You tell me... Am I too much of an amateur for this project?
...

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no, I don't

khstudio said:

...
I must say, I do appreciate all you've done for this project... but I also must say that when things go wrong (as in my case) simple things like voltage charts help determine what & where the problems are
...

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yes. Kevin, you asked me for PCB overlay prints, and you got them, didn't you?

khstudio said:

...
Another problem is, hardly anyone that has completed their unit is visiting this thread & in turn able to help me out.
Thank GOD for lolo-m, Doug & my good friend GUS. ;D
...

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this might be true.

khstudio said:

...
What I can say is... I shared a project with this forum (EQ-3D) & Hundreds were sold & are working.
I made ZERO $$$ off the project but supported it & shared everything I had.

In this case, the Designer is nowhere to be found & it seems like you're left holding the bag.

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mhm, the designer might be on holiday, busy, whatever?
you sure did a great work and support with the 3D EQ,
but with this build / support you are very impatient.
we are not always online and able to remote support a problem within minutes (or hours, or days).

Kevin, you will fix it with no doubts, but be patient.

best
Volker

I'm not impatient... I'm just trying to be on top of it.  
I'm SURE others will gain from my experience... at least with the voltages I got others to post.

I'm sorry man, I DO NOT want to be or meant to sound like a dick.
It's just very frustrating.

I am posting a lot because I need to give readings, etc... so I can get help.

Volker, I'm not blaming you bro. I understand you can only do so much.


Anyway - right now I have 1 channel working correctly & the voltages match others... BUT, I'm STILL getting DISTORTION while compressing!!!  I don't get it & may never at this point.

khstudio said:

Anyway - right now I have 1 channel working correctly & the voltages match others... BUT, I'm STILL getting DISTORTION while compressing!!!  I don't get it & may never at this point.

Click to expand...

How much are you compressing ? If it's more than 20dB reduction you reach the cutoff point of the 6BC8... And you'll have distortion.

PS: every problem has got a solution but sometimes it's pretty long. But I do understand you. I don't make money with this project, I'm working about 20 hours per day at the moment and I'm still trying to make support to this project  (because it is one of the most exiting project at the moment). Yes, some of us should do the same...

khstudio said:

I'm not impatient... I'm just trying to be on top of it.  
I'm SURE others will gain from my experience... at least with the voltages I got others to post.

I'm sorry man, I DO NOT want to be or meant to sound like a dick.
It's just very frustrating.

I am posting a lot because I need to give readings, etc... so I can get help.

Volker, I'm not blaming you bro. I understand you can only do so much.


Anyway - right now I have 1 channel working correctly & the voltages match others... BUT, I'm STILL getting DISTORTION while compressing!!!  I don't get it & may never at this point.

Click to expand...

We are going to look into your situation...I will be talking to Gus later today.

Rowan... That would be great! Thanks... this is a tough one.

lolo-m, I will test to see how deep into compression I'm going when I get a chance.

I forgot to mention, even with just ONE channel hooked up (I just pulled the tubes from one side) my Power TX still got VERY hot!

I'm going to try pulling the tubes from the other channel & do the same test I did last night to see if anything different or strange happens... like with the TX heat & see if the threshold reacts properly, etc...

Channel 2 (last nights test) ALL the voltages looked good & matched others reading... like the R10-330r point = 12.05v.
And unlike earlier test I did with both channels connected, the Voltage @ R10 did NOT move around like it did before... this was the 1st sign of good news.      Why the PT still got hot is a mystery.  I will try to do a "current draw" test for each channel, per Dougs request.

After I get thru all this - I will make a more complete voltage chart showing EACH Cathode voltage & their current draw, Plate voltages (coming into & out of each side of the TX's to the Plates)

I made a voltage chart in EXCEL & a TEXT doc.
these measurements will help others troubleshoot none working units & narrow down problem areas.
Also confirm if your unit is working properly.

EXCEL VERSION = http://www.khstudio.us/DIY/PM670/PM670-VOLTAGE-CHART.xls

PL1 - Control Voltage (Threshold Off, Then 1st ON Position, Med & Full on) This one is tricky but important!
...Must have audio going thru unit, say 1.2v Test tone @ Input (Please measure AFTER connecting to input! due to loading)
& then set gain to have 1.2v at the output (with Threshold fully off)
Obviously everyone's measurements will be slightly off due the differences of Threshold controls, Taper & values chosen...
but if you KNOW your switch & values, posting the value along with the Voltage reading will be more accurate!
((((Sorry... This Test should have been added to the Test Sheet.))))

PLEASE DOWNLOAD & POST YOUR VOLTAGES... Thank You!

Below is the TEXT version & Attachment Version Below that.
------------------------------------------------------------------  
PM670 Voltage Chart USER NAME =
"Inital setup"   input gain & threshold control at 0

Measure voltages referenced to ground - Set RV3 wiper to -2.4VDC - Set RV6 wiper to -4.5VDC

Power Transformer & High Voltage output =
HR* = Heater resistor Value =
Volts - Before & After HR* =
VU METER "Type" =

POWER SUPPLY NOTES
KL1 AC-IN HIGH VOLTAGE AC IN TO DIODES
R1 Before 47r - 2w
R1 After 47r - 2w
R2 Before 47r - 2w
R2 After 47r - 2w

CHANNEL - 6BC8 - Section
PL1 PIN 2 CONTROL VOLTAGE - THRESHOLD OFF
Q1 Emitter "Common node voltage of R1, 2, 3, 4 = 330r"
R2 330r Cathode = V1a
R1 330r Cathode = V1b
R4 330r Cathode = V2a
R3 330r Cathode = V2b
PL2 Pin 2 Center Tap  of T2 - 10k:600 - 136v from R6 / VU Meter
PL2 Pin 1 Outer Tap 1 of T2 - 10k:600 - Voltage to Plates - One side of R6
PL2 Pin 3 Outer Tap 4 of T2 - 10k:600 - Voltage to Plates - One side of R6
PL3 Pin 2 Should be same as PL2-Pin 2 voltage
PL3 Pin 1 136v INPUT - to R6 & VU Meter

CHANNEL - 5687 - Section
R10 330r "Common node voltage of R11, 12, 13, 14"
R11 47r Cathode = V3a
R12 47r Cathode = V3b
R13 47r Cathode = V4a
R14 47r Cathode = V4b
PL8 Pin 2 Center Tap  of T4 - 10k:600 - 245v INPUT
PL8 Pin 3 Outer Tap 1 of T4 - 10k:600 - Voltage to Plates - One side of R15
PL8 Pin 1 Outer Tap 4 of T4 - 10k:600 - Voltage to Plates - One side of R15

Well, I've read the whole Kevin saga a couple quick times now...

Parden me if I missed it, but have you isolated the power supply voltages and checked out the power supply and tested it all by itself?  Have you confirmed that the PS is fine?

Could you post, or repost, those numbers for the rest of us, please?

Your hot Edcor still worries me.  I wonder if it's clue...

I think I've listed my PS Voltages but they seem stable & match what they're supposed to be.

AC in = 272 vac
244 vdc
134 vdc
& heater Voltage is approx. = 6.8v - using a .33/50w resistor.

EDIT - Sorry, this was measured with everything connected.

it's too bad there is no one in your area that you can take it to for a second set of eyes to look at it.

lolo-m said:

khstudio said:

Anyway - right now I have 1 channel working correctly & the voltages match others... BUT, I'm STILL getting DISTORTION while compressing!!!  I don't get it & may never at this point.

Click to expand...

How much are you compressing ? If it's more than 20dB reduction you reach the cutoff point of the 6BC8... And you'll have distortion.

Click to expand...

I'm glad you brought this up.
With a 1.2v input & output signal - As soon as I turn on my threshold to the 1st ON position - the output gain drops about (.6 ) Volt or so... this is a LOT if you ask me.
Keep in mind that my control voltages closely matches other working units.

this is a shot in the dark, but when I was working on my first PM660 I had tons and tons of trouble with the -17V supply, turns out I needed to isolate the PM660 PCB (the one with the tubes) from ground. I am waiting on some nylon screws, spacers and washers to arrive, right now I just have the propped up on little blocks of wood. I also isolated the heater regulator from ground as well. Give it a shot, you never know.

Knarleybass said:

this is a shot in the dark, but when I was working on my first PM660 I had tons and tons of trouble with the -17V supply, turns out I needed to isolate the PM660 PCB (the one with the tubes) from ground. I am waiting on some nylon screws, spacers and washers to arrive, right now I just have the propped up on little blocks of wood. I also isolated the heater regulator from ground as well. Give it a shot, you never know.

Click to expand...

Wow, really?  What type of problems?
Did you ever use an ohm meter to check "What" was actually shorting?

I didn't, but I think the problem was at the corner where the meter connects.

khstudio said:

lolo-m said:

khstudio said:

Anyway - right now I have 1 channel working correctly & the voltages match others... BUT, I'm STILL getting DISTORTION while compressing!!!  I don't get it & may never at this point.

Click to expand...

How much are you compressing ? If it's more than 20dB reduction you reach the cutoff point of the 6BC8... And you'll have distortion.

Click to expand...

I'm glad you brought this up.
With a 1.2v input & output signal - As soon as I turn on my threshold to the 1st ON position - the output gain drops about (.6 ) Volt or so... this is a LOT if you ask me.
Keep in mind that my control voltages closely matches other working units.

Click to expand...

You've got a real problem here. Must I understand pos1 as threshold all way down ? If it is, check / double check / triple check your switch, someting isn't normal here.

Knarleybass said:

I didn't, but I think the problem was at the corner where the meter connects.

Click to expand...

Yes, that's where the -17V trace runs close to the hole. Using a M4 screw here can give you a short...