the Poor Man 660 support thread

[[silent:arts]]

Volker,
I spent a lot of time making a Voltage chart for this project.

Could you PLEASE post a link to it (& that page) on your 1st post?

Also... if you don't mind, I think it may be taken more seriously if you asked others if they could fill out the chart ...

for sure I can post a link. I just did a quick look at the past 4 pages, but can't find it.
could you post the correct link for me?

people, if you have a working PM670 (or PM660) please fill out Kevins chart.

 

[emrr]

Why do people line up the transformers in their builds?.
 
 Look at guitar amps etc often the transformers are at 90 degrees to each other to minimize the coupling.

That's a good question.  I assume it's not been a problem.   Relatively low levels negate issue?  

 

[idylldon]

Why do people line up the transformers in their builds?.
 
  Look at guitar amps etc often the transformers are at 90 degrees to each other to minimize the coupling.

Guitar amps usually have a power transformer, and output transformer, and (sometimes) a choke.  The coupling potential between a power transformer and an audio transformer seems to be far greater than the possible coupling between audio transformers in an application like this.  I've noticed no problems at all when lining up the transformers in this build, and I did consider it during the layout phase.

Cheers,
--
Don

 

[emrr]

Yesterday I finished my version of the PM670

The meters were a bit tricky: I tried Sifam AL22 which I had laying around here, but somehow they didn´t work. After lots of trying I ended up with these 15V DC meters and a custom made scale. I changed R6 for a 5K trimmer and adjusted it for a 15 V voltage drop for full scale reading. One problem though: when both channels compress the same amount that voltage drop is different between both channels, so the meters show different values. ??? Anybody knows a solution?

Regards, Emre

Great look.   I see you went with isolation in the linking circuit.   Be sure to post the timing mods and the linking in the mod thread too.

We should consolidate the various alternate meter schemes into a single place for simple comparison.  

Solution to meter matching.  Not sure.  Readings representative of differing current draw across PL3/1 and PL3/2.  B+ is regulated and will compensate for the total draw, but difference in meter trim/alignment, or combined V1/2 current draw would show a difference on the local level.   Those meters appear to have a mechanical zero trim on the face.  Do the dance between the zero trim, tube matching, the 5K meter trimmer, and possibly RV3 and see if you can get a tighter match between the two channels.  

 

[lolo-m]

Why do people line up the transformers in their builds?.
 
  Look at guitar amps etc often the transformers are at 90 degrees to each other to minimize the coupling.

That's a good question.  Because they don't know to think about this?  I assume it's not been a problem.   Relatively low levels negate issue? 

The varimu in/out trannies can interract themselves without any real issue as they carry the same signal...
The SCamp trannies can interract themselves too for the same reason (even if the signal isn't really the same).

The problem can be interraction between the two channels and scamp trannies / in-out trannies... I did try to put them at 90° without real improovements... Fortunatelly for poeple, levels are low there and they mount the in-out tranfos on one side of the board, and the scamp trannies on the other... This seam to make them be far enough not to have real problems.


And the mounting is easier and nicer like this....

 

[Gus]

You count mount the edcors in a zig zag manner or at 90 degrees.  It would be an easy test to find out how much coupling between transformers.  Drive one with a small solid state amp maybe a 1watt cap coupled to the transformer not connected to anything else.  Connect a scope to another transformer not connect to anything else and move it around by the transformer being driven with a test tone.

 

[Kingston]

Thanks for the tip about coupling. I will try on mine when I get there.

I've used these edcors in a number of projects, and actually measured the noise floor in them. They seem to be prone to picking noise distance-wise only, and for whatever reason, orientation has far less effect. I would recommend to install these in the opposite side to PSU transformer inside the case, possibly in the case wall. That should be enough.

Although I should say I have not noticed any ill effects with coupling between just two edcors. In G9 for example, these edcors as output transformers have negligible coupling (something like -95dB crosstalk) even if they are side by side, 2 cm apart.

 

[veermaster]

@69er: Those meters can be found at conrad.com odernumber 108480 - 62

 

[veermaster]

Out topic little question : Isn't your slower attack setting dividing the maximum gain reduction by 2 ?

Just checked it: When Attack is at slowest setting and Release at fastest the amount of GR is reduced about 6dB, but at the faster Attack settings all is fine

 

[veermaster]

Love your frontpanel, great color, meters and layout!!

...But what's up with this model 666 ? 

Thanks mate!
You know this thing is EVIL  ;D

 

[Holger]

Emre, wonderful look...
I really like the color ;D
I am going to finalize my baby, maybe another two weeks...

 

[khstudio]

Volker,
I found it on page 75, 7 posts from bottom. Thanks. ;D

If you or anyone has any more test points or procedures that you feel should be added or changed, Please let me know & I'll fix it up.

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

 

[khstudio]

veermaster,
Great job, I really like your faceplate design... meters are cool too.
It would be great if you could fill out the voltage chart.  ;D

 

[veermaster]

Do the dance between the zero trim, tube matching, the 5K meter trimmer, and possibly RV3 and see if you can get a tighter match between the two channels. 

Thanks emrr,
I followed your advice and swapped tubes (6bz7) to find two sets that make for a tighter match between both channels.
This makes me  ;D

 

[veermaster]

veermaster,
Great job, I really like your faceplate design... meters are cool too.
It would be great if you could fill out the voltage chart.  ;D

I downloaded your chart and will fill it out tomorrow...

 

[guavatone]

Nice work Don!!! 
You always seem to have the most unique enclosure ideas.  Old radio surplus?

 

[idylldon]

Volker,
I found it on page 75, 7 posts from bottom. Thanks. ;D

If you or anyone has any more test points or procedures that you feel should be added or changed, Please let me know & I'll fix it up.

In the power supply, R2 should probably be R8, right?

I've filled out the chart and have attached it.  Since I have a stereo unit, I separated L/R measurements with a /.

http://www.mediafire.com/?yjzqt3mztzr

Cheers,
--
Don

 

[idylldon]

Nice work Don!!! 
You always seem to have the most unique enclosure ideas.  Old radio surplus?

Thanks!  I started building tube guitar amps out of old PA heads many years ago, so I've collected a lot of them from the 40s and 50s.  Many of them were trashed as amps (already gutted, major parts missing, etc.), so I sometimes use the old dogs and give 'em a new life with other circuits.  Also, I LOVE the look of these things, which is kind of art deco, bulletproof-industrial!  There's something about that age of American manufacturing that has always appealed to me.  I think a lot of things came together concerning design and implementation during the time period right after the war.  Stuff was built to last while being aesthetically pleasing.  There was a unique mixture of form and function that I can't say I see as much of today.     

I'm also a real aficionado of hammertone paint!  I'm sure glad a couple of companies still make it.  It's almost like a resin coating once it hardens, and it's MUCH tougher than regular paint. 

Cheers,
--
Don

 

[khstudio]

Possible BAD TUBES I'm using

PHILIPS ECG 5687WB (NOS) From Antique Electronics Supply
BLUE Lettering - DATE CODE 8652 = 1986 (December I think?)

Could everyone PLEASE check to see if you are using "These" exact tubes?
& PLEASE - Post the exact tubes you are using in your working units!!!

I just got off the phone with Gus & shared all my measurements & it seems this batch of tubes MAY be wrong or way out of spec.

Forget about everything I posted before & focus on this:
With one 5687 tube installed in the output section I get approx. = 11.5v @ R10 / 330r
This matches what others have posted...

When I install TWO 5687's in the output section I get approx. = 22v @ R10 / 330r  
This is double the current draw, etc...!

I have 8 of these tubes & the ALL do the same thing.

For those of you following my post... this could be the reason why:
#1
my Q4, IRF820 in the PS was VERY HOT!
#2
this could also be the reason why, when I turned my "threshold" pot to the 1st on position, I would lose about half my signal level by "possibly" hitting the sidechain way too hard.

 

[idylldon]

TUBES I'M USING

PHILIPS ECG 5687WB (NOS) From Antique Electronics Supply
BLUE Lettering - DATE CODE 8652 = 1986 (December I think?)

Could everyone PLEASE check to see if you are using "These" exact tubes?
& PLEASE - Post the exact tubes you are using in your working units!!!

These are the exact tubes I have in my 670, and I bought them from AES as well.  I just tested the six I bought on my Eico 666 (the mark of the BEAST tester), and they were all pretty close to one another.  

Yes, the "8652" means they were made in the 52nd week of 1986.  Heh, maybe you got some bad tubes due to someone partying too much during Xmas week!

Cheers,
--
Don