the Poor Man 660 support thread

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hello to all!
have some question for you guys who finished buildin this project.
how much will be the cost for all the parts to build this?
how is this finished monster sounding? anyone care to post some clips?:):)
thanks in advance!and sorry for my bad english
Martin.
 
khstudio said:
I was thinking along the same lines... 12v heaters = less current draw.
BUT - I don't think the 9v secondaries of the Edcor will cut it... we need more juice.

Exactly, just put another 9V 6A tranny in there and be done with it...maybe another bridge as well.
 
Hi,
i also have the edcor PT and it gets hot like it should...(stereo unit)
actualy the whole box gets very warm....but i wouldnt call the fire fighters yet...:) - my bandmaster amp PT gets much hotter and its a fender design so....
kev - maybe you should consider mounting the PT outside of the box - like on the back panel.

just my 2 rupis...
 
do you have a clamp on ammeter?

just put all the tubes in, with everything stone refridgerator cold at 4 in the morning, measure the primary current after a 5 minute burn in.

then unplug the beastatron, measure the primary resistance.

then apply ohms law for heat, which will be primary current times primary current times primary resistance.

see what you get.

this is inexact science do to all the pwr factor voodoo and mag currents vs saturation  levels, but it should give you an idea if you are pushing the copper beyond it's current carrying ampacity.

then pull all the tubes, put the ammeter back on the primary, get a piece of paper and draw an x-y graph with primary ac current  vs tubes put in.

you do not want to mess with breaking the B + line and inserting a ammeter, bad things seem to happen when i do this, like expensive meters fryng.

we just want to see if as the tubes are inserted, all of a sudden there is a jump in pri current.
this would indicate saturation, which means the lams will generate heat as well as the
copper loss.

ok, here is a faster, safer and easier way.

wire in a light bulb socket, 120 style lamp socket for your house, get a nice ceramic one from china, wire in a 120 watt bulb in the pri circuit.

then remove all tubes, insert them one by one, and see what the bulb does. 
 
When trying to fill out Kevs Voltage Chart I shorted R1 on the PSU to Ground (Tip of DigiMeter touched R1 and R6) so now my High Voltages are not correct anymore.
Which parts should I check/replace first? I guess it´s one of the transistors?
Thanks all, Emre
 
Sorry to here that man... there should be a disclaimer on measuring.
There's a lot of "Close" components that can short when checking voltages.
Test points would have been a nice added feature.

I'm sorry I don't understand the PS enough to give you some tips to fix it... man that sucks.

 
It´s alright Kev, I don´t blame it on you  ;)
Actually it makes me even laugh, damaging my working unit while just checking some voltages...
I know I will get it to work again sooner or later, I´m not in a hurry.
Hope you solve yours as well!
emre
 
Emre, that's a bummer but easily done.
I did it to a Telefunken 676a whilst testing voltages due to some "crackling"
Screwed the board and some vintage transistors ..... never got it working again
...... yet !!

MM.
 
Emre...have you measured R1 (in circuit)? And while you're ad it, measure R6 as well.
I've had a similar accident where R1 kind of blew..and became 4M/ infinite resistant.

 
Hey guys...

Just wanted to pop in and see if any of you have any troubleshooting tips...  With a lot of help from my buddy Geoff, I have what resembles a working PM660 minus it actually working  ;) ...  It powers on (no explosions!..just lost the lamp though) and passes audio.  Channel 2 is out of phase, and it has very low headroom.  It's sort of hard to tell if it's really compressing or not..(it's doing something)... Setting 6 on the time constant seems to be the cleanest, but still distorts if you hit it with any sort of real signal. 

The phase issue is something I think I can handle, but do any of you have any suggestions for the headroom issue?  I swapped some tubes around and that solved any differences between the 2 channels.  So at least things are consistent on both sides. 
 
Undercarriage,

The first thing to check would be the voltages.  There are some charts listed earlier in the thread with the voltages from working units. 

Cheers,
--
Don
 
idylldon said:
The first thing to check would be the voltages.  There are some charts listed earlier in the thread with the voltages from working units. 

We've got all the stock voltages nailed (tube heater was 6.2v if my memory serves me well).  I don't think we've worked on the unit since khstudio's issues have come up, so we could probably stand to go through all the other voltages listed.  This is a non-pimped unit, so all the wiring has been done according to the diagram in the first post. And it's stereo (pm670).

Here's where maybe something went wrong.  We used the XLS file to calculate the R values for the rotarys (like I imagine everyone has) - I noticed though that turning up the gain switch doesn't always result in an increase in gain - especially up at the top end.  Anyone else see anything like this?
Also, how are the working units for headroom?  Will they take a lot of input?

I feel like an idiot for asking, but I've seen the question a whole lot more than I've seen the answer - what size should the fuse be?  I think we used a 6 amp slow.

Thanks for the tips.
 
We used the XLS file to calculate the R values for the rotarys

I used the same thing & I don't have any issues like that... Gain change is very consistent throughout.

I can't say for sure but I think a 6 Amp fuse is too big... I think I have a 2 or 3 Amp in mine.

Double check your Gain control on it's own, disconnected, with an ohm meter to make sure both decks are correct & match each other.

When checking your voltages PLEASE be careful... there's a lot of close components that can & will short out, some of which are HIGH VOLTAGE & will cause damage!
 
Quick question before i switch on my 670 and it goes bang.
I've an Avel Lindberg LLLPM670 power transformer which has an 'interwound screen conection'
i'm assuming this goes to my star ground and is the same as the 'static shield' on the PM wiring diagram?
thanks :)
 
khstudio said:
kazper said:
Whats the Data sheets call out for the current on the valves?

6BC8 = 0.4A
5687 = 0.9A
x4 = 5.2A

Where running it at 86%.

Any chance we could skip the Resistor on the 5687 and give it higher voltage, it's specked to 0.45A on a 12.6V heater?

I was thinking along the same lines... 12v heaters = less current draw.
BUT - I don't think the 9v secondaries of the Edcor will cut it... we need more juice.

Since the PM670 cooks eggs AND coffee at the same time, I opted for 12.6VDC heater regulation. I had the PSU toroid custom made so this was easy. I have 15VAC, 4A winding for heaters. This gets regulated to 12.6VDC. Less lost watts, and less heat.

The two channels are still eating 6,3VDC (2,6A) each, but the channels are wired in series from the regulator. So that's 2X4 tube heater series/parallel configuration, eating 6,3VDC (2,6A) per channel, or a total of 12.6VDC (2,6A) depending on which way you look at it.

If one tube fails, voltages get knocked very little (25%), so there not much danger in doing the above.

Although another prodigy pro member warned of a theoretical possibility of one tube heater shorting in either channel (might not be possible?), which would result in one channel seeing the full 12,6VDC. A death of four tubes. I'll eat that risk.
 
Can someone point me in the direction of the heater PSU schematic. (Link on the first page doesnt show it.)
Nearing the end of my preflight checks ;D
 
DC Power = VDC X amps.

Some numbers for simple math  

12VDC x 2amps =24 watts

6VDC x 4 amps = 24 watts

12.6 volt or 6.3 volt wiring of the fil still equals the same watts.
 
Gus said:
DC Power = VDC X amps.

Some numbers for simple math  

12VDC x 2amps =24 watts

6VDC x 4 amps = 24 watts

12.6 volt or 6.3 volt wiring of the fil still equals the same watts.

if that was somehow related to my PSU choices,

15VAC to 12.6VDC 2.6A is going to be somewhat easier on the regulator IC versus 9VAC to 6.3VDC 2.6A.

the main point is that I get to do the heater with just one regulator, where most here are using two LM338T based circuits (rated 5A max each). Less heat generated in a more optimal setting.

[edit]

nevermind,
I guess your comment was really for the guys planning "less current draw".
 

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