the Poor Man 660 support thread

[idylldon]

Good idea... I was wondering when I saw your pics what they were for.

When my father-in-law moved out of his house and into a condo, he gave me a ton of all types of connectors he had collected over the years.  I figured since I had these small test points that I might as well I'd use them. 

Your unit is very cool BTW.

Thanks!  I really like the old PA heads and try to use them whenever I can.  There's something about that era that was pretty stylish, IMHO. 

Cheers,
--
Don

 

[khstudio]

Well, all is going well (except for the HEAT).

With the EDCORE Power TX, I had to drop the Heater resistor from .47r to .33r
now my heater is about 6.19v... not too bad.
This is also with a 6.3v BULB connected!

I'm having another strange issue that I remember reading but can't find it.
The needle of the Meters moves around randomly when I change the Threshold... it's like a magnetic field thing going on.
I tried putting the lid on but that didn't help.  :'(

What to do?

 

[khstudio]

Well I'm up & running but I've got problems & don't get it.
One channel almost works OK but I'm getting distortion when it's compressing.
... been looking it over VERY carfully for hours & can't find anything wrong.

About RV3 & RV6...
The voltage I measure changes when I change the threshold???
Is this normal & if so... where should they be set to adjust the voltage correctly?

 

[khstudio]

Damn. I just let touched my EDCORE Power TX & it's REALLY HOT too.  

I know a lot of current is being drawn but I've got a lot of guitar amps & none of the Power TX's get that hot.
This sucks.

Can I just unhook one PCB without any issues?
This may help narrow down the problems.

 

[khstudio]

Sorry to ask (if it's already been asked) but is there a "Voltage Chart" floating around to help with my trouble shooting.
I'm loosing my mind with this one. Sadly, I see nothing wrong & hope it's not been a waist of time & $$$.  :-\

Any help would be very cool.

Ohhh... I guess I should mention that the "AUDIO" going thru the unit sounds & seems to work well ... it's when I try to dial in any amount of Compression that random  things on both channels start happening =  distortion, meters react weird, etc...
I am able to get a little usable compression out of ch1.

 

[[silent:arts]]

check if the Audio transformers are wired correct (we have seen this mixed up before)
check all taps of the audio transformers (we have seen some broken ones)
we have also seen this behavior with bad solder joints at the rotary switch.

if you want to disconnect one side make sure to change the heater resistor.

 

[khstudio]

Thanks Volker.

Well. it's a new day with a fresh head.
I tested ALL my tubes & they measure good.
The Power TX does get VERY hot but it takes about a half hour to get there... any ideas on this or should I worry about it?

I broke out my scope to check the audio path & it looks pretty good & it's compressing.
This was VERY interesting to be able to "See" the release times on the scope!!!
I have a switch set up for six settings:
1)  2u + 68k
2)  2u + 180k
3)  2u + 470k
4)  2u + open
5)  Blank
6)  STOCK - 10u

Since the stock setup goes thru the 10u First, Then thru the 10k POT... I decided to leave the pot in that position & be able to use it with ALL the setting for an added effect. It's pretty cool.

In "Stock" mod, the release is VERY SLOW!!!!!!!!
(anyone else notice this??? )

I like the "Blue Bird" values of 2u + 68k but adding the other values are very useful.
I also think the Distortion I'm hearing (only when compressing) is like Bluebird described... I may try the tube change too.

OK, what I notice on the scope is that, as SOON as the threshold is kicked on the 1st setting (mine is set up LOG Taper) it knocks off aprox .6 volt! This seems like a LOT to me. Yes my pot is set up correctly (measured & double checked)
This is where a "DC Threshold" would be useful.
Any ideas on how to back this down?

Last update,
My meters are still reacting very strange... like a magnetic field.
What should I do about this???
Maybe use shielded cable on the VU send & return lines?

What's also strange is each meter seems to react to the opposite channels threshold (channels Un-Linked)

Time to take it off the bench & re-listen.

 

[[silent:arts]]

since you did some mods I would suggest to leave them out first :-*
guys, build it like it was intended, check if it is working.
than you can mod and do everything you want.
but please let this support thread be up to the original version.

 

[khstudio]

Understood... BUT
The switch I have completely bypasses any mods & makes it STOCK.

Any answers to my other questions???

 

[khstudio]

Here it is:

NOTE: I have a STEEL plate that separates the PS from the rest of the circuit that is not in these pics.
I also didn't install the RELAY PCB yet.

 

[khstudio]

I could really use some help with the (unanswered) questions I've posted earlier... anyone.

Power Trans HEAT = about 60 Deg C / 140 F    (or more) !!! EDCORE Power TX !!!

Also, The trimmers & their voltage adjustment & how it CHANGES which different "Threshold" settings, so... where should the Threshold be when adjusting???

Etc...........

 

[Knarleybass]

YES, the heat builds up in my 660's build up and eventually the heater PSU shuts down. I don't know what to do.

 

[khstudio]

It's my PT I'm really concerned about.

OK... I removed my time constant switches & wired it TOTALLY STOCK!
I have the SAME problems.  :

I'm really stumped here.

The 2 BIG noticeable problems are:
When I move either channels "Threshold" control, the other channels meter bugs out & jumps all the way up.
I'm also still getting a **** load of distortion BUT ONLY when compressing.

The signal amp section seems to work & sound pretty good.

I've checked ALL connections several times.
Voltages & trimmer set too.

 

[emrr]

I don't have a built unit to consider here, and can't address distortion from any informed POV. 

Is heat measured with lid on, or open?  If open now, lid on will only get worse.  But 140 ain't so bad.  I always argue for old-style mounting of components on the back rear if possible.  Confirm current draw is correct.  Add a fan if you can, drill a ton more holes for air flow, etc. 

Try diode isolation of the two channels from respective PSU points (won't be simple), it may or may not help channel interaction.  There seem to be lots of comments about meter interaction, and no diagnosis or clear commentary.  There's always the unstuffed filter cap holes on the amp boards, which might also provide a teeny tiny bit of extra stiffness and local filtering.  Even though they are in parallel, they are still isolated by location and wire interconnection.  Meter movement is only indicative of one thing; a change in current draw. 

 

[Kingston]

about PSU transformer heat.

I was recently given a bit of insight into how to specify a PSU transformer for projects like these. Turns out the heater part of the PSU specs that are floating around here are severely underrated. They run far too close to specified maximum (max 6A winding running at some 5,2A). It means the transformer is going to get HOT and the core will start to saturate.

If you don't want to cook eggs with your PSU trafo in a situation like this I was told you should rate the required current to about 60% of the maximum for the winding. In this case, the 5,2A should be pulled from something like 8A max rated windings. Otherwise you're in for core saturation effects, heat, and transformer "singing".

 

[mikeyB]

about PSU transformer heat.

I was recently given a bit of insight into how to specify a PSU transformer for projects like these. Turns out the heater part of the PSU specs that are floating around here are severely underrated. They run far too close to specified maximum (max 6A winding running at some 5,2A). It means the transformer is going to get HOT and the core will start to saturate.

If you don't want to cook eggs with your PSU trafo in a situation like this I was told you should rate the required current to about 60% of the maximum for the winding. In this case, the 5,2A should be pulled from something like 8A max rated windings. Otherwise you're in for core saturation effects, heat, and transformer "singing".

Bit of a bummer for the Edcor buyers - Kevin - why not slap in an off the shelf 50VA toroid for the heater windings - move your psu pcb forward and stand the toroid on its edge between the edcor tx and psu board, that way your edcor will run cool supplying the ht and +/-17v - just a thought!!

 

[radiance]

rate the required current to about 60% of the maximum for the winding. I

That's pretty basic stuff if you ask me.
And kind of sad for all those people who have participated in transformer group buys without having access to the schematics to check whats actually needed. Someone clearly did not do his homework here....

I'll defenatly go for a separate heater transformer. Don't trust this thing beeing on 24/7 as is....

 

[[silent:arts]]

about PSU transformer heat.

I was recently given a bit of insight into how to specify a PSU transformer for projects like these. Turns out the heater part of the PSU specs that are floating around here are severely underrated. They run far too close to specified maximum (max 6A winding running at some 5,2A). It means the transformer is going to get HOT and the core will start to saturate.

If you don't want to cook eggs with your PSU trafo in a situation like this I was told you should rate the required current to about 60% of the maximum for the winding. In this case, the 5,2A should be pulled from something like 8A max rated windings. Otherwise you're in for core saturation effects, heat, and transformer "singing".

wrong. this will be different from manufacture to manufacture. a good one will calculate the needed headroom.

That's pretty basic stuff if you ask me.
And kind of sad for all those people who have participated in transformer group buys without having access to the schematics to check whats actually needed. Someone clearly did not do his homework here....

can't remember any Edcor PSU group buy, all other (four) group buy PSU transformer seams to be fine.
and here is a link to a working unit with an Edcor PSU transformer:
http://www.groupdiy.com/index.php?topic=28274.msg407709#msg407709

 

[[silent:arts]]

OK... I removed my time constant switches & wired it TOTALLY STOCK!

good

When I move either channels "Threshold" control, the other channels meter bugs out & jumps all the way up.
I'm also still getting a **** load of distortion BUT ONLY when compressing.

I know this is a long thread, but my memory is we have had covered this before.

 

[Knarleybass]

I am using the Avel lindberg toroid for my 660's the rating for the heater psu is 6.0A, is that enough? would that be the cause of excessive heat on the LM337?
  current draw for the tubes, power light and bypass Led is 2.6A