the Poor Man 660 support thread

[stitch-o]

Hello forum!
I finally got around to wiring up my 670.
Very psyked!

Two questions to get me over initial hurdles:
I have Avel Lindberg 087539 and I cant find the color code for the leads.
I think white and orange go to heater rectifier,
black and black are the 250VAC secondaries,
and grey/brown tied and blue/purple tied are primaries to mains AC.
That leaves green (ground?) red and yellow...
Are these correct and what are red and yellow?

I have 6 pos rotary switches for the time constant.
Are these going to be made to be like 5k pot? log or lin?
I think I have a spread sheet to get resistor values for the 6pos switches.

Cheers and thanks!

-s

 

[shabtek]

datasheet

 

[stitch-o]

datasheet

perfect!
So red and yellow are 250VAC secondary.




Cheers!

-s

 

[stitch-o]

Bout 99% finished.
Waiting on a replacement edcor transformer then is done!
Here are some build pics:

Triple checking PT sec. wiring to PS PCB.
These are correct?

Cheers and thanks all!

 

[dagoose]

I also posted this in the M670 topic, but since this one is more alive I crosspost it here as well:

As a nice 'making it through wintertime' I want to start redoing my (hardly used) PM670.
I was wondering about the 5687 tubes, I used it with 1 tube in the sidechain because it was hard to get it right. But now I wanted to start using all 4 of them again but found out that one of the tubes is gone.. 
So.. what are good 5687 tubes to go for right now that don't pull 20.000 of amperage and get to 23.000 degrees. 
What source do you have for 5687 tubes that are good?

 

[stitch-o]

I also posted this in the M670 topic, but since this one is more alive I crosspost it here as well:

As a nice 'making it through wintertime' I want to start redoing my (hardly used) PM670.
I was wondering about the 5687 tubes, I used it with 1 tube in the sidechain because it was hard to get it right. But now I wanted to start using all 4 of them again but found out that one of the tubes is gone.. 
So.. what are good 5687 tubes to go for right now that don't pull 20.000 of amperage and get to 23.000 degrees. 
What source do you have for 5687 tubes that are good?

Hi dagoose,
Here's my list of good tube stores:
http://www.thetubestore.com/
http://www.kcanostubes.com/
http://www.tubemonger.com/
There's a guy on Gearslutz named Bowie that has nice tubes as well.

I just got final edcor and a few random resistors to replace in mine before I sit and run through paces,
but I am already reading all the mod/sidechain threads on this comp.
Already pretty sure I'll replace the input and possibly output transformers.

Does anyone have a stock 670 working fine?

 

[duantro]

Hi dagoose,
Here's my list of good tube stores:
http://www.thetubestore.com/
http://www.kcanostubes.com/
http://www.tubemonger.com/
There's a guy on Gearslutz named Bowie that has nice tubes as well.

I just got final edcor and a few random resistors to replace in mine before I sit and run through paces,
but I am already reading all the mod/sidechain threads on this comp.
Already pretty sure I'll replace the input and possibly output transformers.

Does anyone have a stock 670 working fine?

Mine worked fine stock, however I found the edcor input transformers a little grainy sounding.  Really happy with the  cinemag inputs, and the Kingston mods now.

 

[dagoose]

Hi dagoose,
Here's my list of good tube stores:
http://www.thetubestore.com/
http://www.kcanostubes.com/
http://www.tubemonger.com/
There's a guy on Gearslutz named Bowie that has nice tubes as well.

I just got final edcor and a few random resistors to replace in mine before I sit and run through paces,
but I am already reading all the mod/sidechain threads on this comp.
Already pretty sure I'll replace the input and possibly output transformers.

Does anyone have a stock 670 working fine?

Thanks!
But they are all USA, wanted to have them from the EU so I found a set of sylvana 5687's on ebay in the EU.
In the beginning I had mine stock, later on added the  scamp mod and pulled one of the 5687's because it was simply hard to get it right.
Since then, it has been used as a really expensive rackfiller which is a shame.
So... during this winter, I will replace the IO tranny's (I think I go for ll1676)
This is what mine (without teh scamp) looks like https://groupdiy.com/index.php?topic=28274.msg415199#msg415199
I will also redo my panel, don't like the fake fairchild look..

 

[stitch-o]

Thanks!
But they are all USA, wanted to have them from the EU so I found a set of sylvana 5687's on ebay in the EU.
In the beginning I had mine stock, later on added the  scamp mod and pulled one of the 5687's because it was simply hard to get it right.
Since then, it has been used as a really expensive rackfiller which is a shame.
So... during this winter, I will replace the IO tranny's (I think I go for ll1676)
This is what mine (without teh scamp) looks like https://groupdiy.com/index.php?topic=28274.msg415199#msg415199
I will also redo my panel, don't like the fake fairchild look..

Hi Dagoose,
Heres a few European tube venders...
http://www.vacuum-tube-shop.com/index.php?url=info
http://www.watfordvalves.com/
https://www.tube-town.net/
http://www.drtube.nl/
http://www.hotroxuk.com/

 

[stitch-o]

Mine worked fine stock, however I found the edcor input transformers a little grainy sounding.  Really happy with the  cinemag inputs, and the Kingston mods now.

Great to hear!!
I'm opening my comp today to finish small tweaks and start assessing for the mod.
Is there any concise list of parts and steps/instructions for the Kingston mod?

CHEERS!

Main Board Edits:
-T1 and T2 replace Edcor for ll1676
-600 Ω T pad feed forward/feedback switch
-4.7uf to low side audio on primary T2
-Sidechain HP switch fed from primary of T3 (2kΩ resistor and 2 x 2.2uf film)
-15k trimmers at T1 secondary to 4.7kΩ resistors
-R5 to 4.7kΩ resistors. 150-200V rail attached between 4.7kΩ resistors from CT of T2
-R6 22kΩ to 100R trimmer
-15k trimmer at secondary of T3 to 25k trimmer
-R15 to 2 x 10kΩ 3W resistor. 250-300V rail (add 100R in series, 10uf to ground) from CT of T4 to between R15A and B (10k 3W)
-4.7uf to low side audio on primary T4
-Q1 from 2N6107 to D45H11
I see the link switch edits and will have to research a bit more as to the why and how...

Can I leave the time constant to original PM design and not have issue?
Would it be acceptable to use Edcor and not attach the CT?

 

[duantro]

Great to hear!!
I'm opening my comp today to finish small tweaks and start assessing for the mod.
Is there any concise list of parts and steps/instructions for the Kingston mod?

CHEERS!

Main Board Edits:
-T1 and T2 replace Edcor for ll1676
-600 Ω T pad feed forward/feedback switch - would T-pad pot replace the Input Gain rotary switch or would this be a variable selection? T pad replaces input rotary switch
-4.7uf to low side audio on primary T2
-Sidechain HP switch fed from primary of T3 (2kΩ resistor and 2 x 2.2uf film)
-15k trimmers (or is this the input gain rotary switch?) at T1 secondary to 4.7kΩ resistors I don't see this, but think it is the input switch and not needed
-R5 to 4.7kΩ resistors. 150-200V rail attached between 4.7kΩ resistors from CT of T2
-R6 22kΩ to 100R trimmer
-15k trimmer at secondary of T3 to 25k trimmer this is the output attenuator rotary switch
-R15 to 2 x 10kΩ 3W resistor. 250-300V rail (add 100R in series, 10uf to ground) from CT of T4 to between R15A and B (10k 3W)
-4.7uf to low side audio on primary T4
-Q1 from 2N6107 to D45H11
I see the link switch edits and will have to research a bit more as to the why and how...

Can I leave the time constant to original PM design and not have issue? yes, set up time constant how you like
Would it be acceptable to use Edcor and not attach the CT? I need to double check here, but I think I did this. It's been a while since I've done these mods

I've tried to comment in blue here on my thoughts. This probably should be moved to the m670 thread, no?

 

[crisotop]

I cannot believe it, my PM670 is finally alive after years of struggling with the PSU. Many many thanks to all the contributors and especially Paolo aka "ppa" for the PSU mod.

still struggling with some random click sounds when I have both channels running at the same time, and a low heater voltage around 5,6V from the slow start boards under load. Will browse through the last 50 pages, if anyone already had similar issues

 

[justinheronmusic]

I read earlier that the XPWR063 is under spec'd, and wrong for this project. Is this true?
Does anyone have a completed and working PM670 with the Edcor XPWR063 that is stock?  If so, what changes need to be made to the PSU if any?

Also, is it correct to say that there are two input transformers per channel? I am not totally sure how the transformers are being used in this circuit.

Do the main boards have to be 1/2W resistors or can I use 1/4W on them? I've got 1/2W on in the power supply and it is pretty tight/cramped.

 

[alexc]

The edcor xpwr063 is not under-spec'd for the pm670 stereo limiter build - I've used it in several big limiter builds with no probs.

The supposed issue is that the edcor heater winding, rated at 9Vac @ 6A is isn't sufficient for the pm670's stock requirement of 5.2A @ 6.3Vdc  heater current.    ie.  4x5687 tubes (3.6A total) and 4x 6BC8 (1.6A total).

I would however, note the following wrt the 'stock' pm670

i) the edcor primary is 2x 120Vac windings, which makes for 120Vac or 240Vac  (50Hz as I used it) line voltage.

      -- if used at 110Vac, the output voltages may be somewhat lower than rated

ii) the edcor psu traffo  is a big unit, making it challenging to locate with sufficient isolation in a single rack build

      --the pm660 has alot of stuff in there, including many wires, 2 pcb modules, 8 signal transformers etc
      -- best mounted outside rack, back panel  if possible

iii) the edcor psu traffo  radiates em fields pretty well, as one might expect in a unit rated at 135VA or so and working hard   

      -- a major issue in the stock pm670 because all the signal traffos are unshielded and in close proximity
      -- try to locate the signal traffos as far from the psu traffo as possible!! 
      -- leave the final orientation  of signal traffos open until the testing phase. It makes a BIG difference to the noise floor

iv)  I strongly recommend using the Rondo company toroid (same spec as edcor)

        -- it had a significantly reduced amount of noise radiated from the psu traffo into the signal (and sidechain) taffos
        -- physically less massive so making internal mounting more feasible than Edcor
        -- I ended up keeping the Rondo for the pm670

v)  usage of toroid with some magnetic shielding for can improve the noisefloor further
 
        -- I used 2x 'the Don' toroid shielding strips with the Rondo and measured 3dB improvement on noise floor hum

vi) fault conditions in the heater circuit can cause overload current to flow and stress the heater winding

      -- imho keep heater circuit reasonably simple (no regulation) - there's already plenty going on!

So to summarise :

The Edcor xpwr063  is a good unit and can be used successfully in a single rack pm670 build but it is more challenging than with the Rondo toroid to get acceptable noise floor performance.

Noise performance is everything in a tube limiter build!

 

[alexc]

Also, to answer some of your questions,

i) the pm670 is dual channel in stock form with 2 signal transformers and 2 sidechain transformers per channel.

So the stock configuration uses 8x edcor xsm transformers all up.

ii) the pm670 stock works fine if properly built

However ....

i) The PSU pcb module can be a problem for some, especially if manhandled

I built several psu pcb modules (around 4 all up) - on my most abused one (first one built) I ended up having to use the psu mods suggested by member pier paulo. His mods for extra device protections brought it back to life and remains fine to this day.

The remaining 3 units are all stock, with the exception of one of the film caps - changed to a larger one as described in this thread.

Extreme care needed to replace small signal transistors if blown -- lifting traces very much an issue

ii) the 10uF time constant film cap is not really useful - most people tend to modify the timing circuit connector on the signal pcb module and add an external rotary switch with caps/resistors

iii) cooling the unit is important : I recommend 3ru chassis with ventilation and mounted in rack with seperation from other units to promote air flow. In hot climates, a cooling fan may be beneficial. (I'm in a cold climate).

iv) tube rolling the 6BC8 with other types is not recommended : the 6BC8 has a low-ish heater current, some subs are higher. The last thing this build needs is more heater current requirements!

v) I don't recommend 0.25W resistors in the psu, generally speaking

 

[alexc]

The basic mods that I recommend :

- use Rondo toroid with some shielding strips from 'the Don' or a toroid can (ebay)

- build a spare psu module 'in case'  8)

- sub the signal input transformers with something shielded  and cleaner sounding,  like a cinemag/jensen/sowter 600/10K
- sub the output signal transformers with Carnhill 9600/600

- use rotary switch for the 'Level' control - I like the ' Ural 24 pos dual deck rotary' from ebay and would like to try a 'prebuilt stereo attenuator' version that you can get on ebay. Around 25K log response  is needed. 

Note that the 'direction' of attenuation may be reversed on a pre-built unit  (small price to pay for a well assembled unit in this critical component)

- you can use a good quality dual-deck potentiometer for 'Threshhold', like an Alps Japan unit, again 25K log or so

- locate the 'meter zero' adjust pots to the front panel - these are adjusted often

- mod the signal pcb module timing circuit for an external rotary switch-plus-caps for major improvement in flexibility

Optional mods I recommend ...

- if adding VU metering, use a buffer pcb (like jlm vu buffer) - bridging outputs with an unbuffered VU meter adds plenty mid-range distortion!

- add some additional capacitance  to the heater circuit and mount the 'heater dropping resistor' on the chassis

 

[crisotop]

Just to let you know -- I substituted the original spec'd 6bc9 with 6n5p and my random clicking sounds and weird compression behaviour went away. Not sure if I damaged the original tubes during build / troubleshooting, but the simple swap got rid of all my problems. Will now try different timing mods using the SCAMP booster to finish the unit of.

 

[alexc]

The 6N5P can be a good sounding sub for the 6BC8 - I used it for a while before going back. I ended up thinking the stock tube was smoother and I was happier with the lower heater consumption.

 

[justinheronmusic]

Another 8hrs or so of use in my studio. No probs at all.

I am trying out different tc networks. The bluebird mod is now 2x 6pos switches
with 0.22uF, 0.5uF, 1.0uF, 2.2uF, 4.5uf and the onboard 10uF on one switch and
26K, 68K, 150K,220K, 470K and OC on the other, in place of the stock series 10uF and 10K pot.

I am using mostly a parallel 220nf and 26K. It's very fast release - maybe 0.25s or so.
Not sure of the attack, but it seems moderately quick.
The responsivess is there all right. Just fantastic.

If I wanted to keep the stock attack time, but mod the release times, I could wire the TC network in parallel with the stock 10uf and just vary the resistors, is this correct?

Forgive my Noob question but what would be the best way to wire the TC in parallel from the stock design? Would I need a different switch than the 6 pos Lorlin that I have here?

 

[Kingston]

And for the love of god, do not - I repeat - do not use rotary switches anywhere in the signal path of this plan. This means the 10-50k dual attenuators of both the input and sidechain.

I still have horrible nightmares troubleshooting completely haywire channels where the 24-step shitbags had gone bad. These were the famous ISS-proof Elma rotary switches. Yes, The International Space Station. Having these pieces of **** controlling life support would not be my first choice to be honest.