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Trouble with Rod Coleman DHT reg

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C

cowneko

Member
Joined 2013
Hi everyone,

I'm converting my raphaelite CSK30 to monoblocks and I wish to integrate the rod coleman regs V7 I assembled some months ago.

I'm in the testing phase and I encounter a strange behaviour, seems like not enough current is fed to the reg, witch seems odd.

My PT is a PW300ABA-230 from raphaelite

390V - 320V - 100V - 0V - 320V - 390V at 300mA
5V at 4A (for the rectifier)
6.3V at 4A ( for common input pentode tubes)
2X 5V - 2.5V - 0V

I decided to wire the two 5V secondaries in serie to obtain 10V at 4A witch should be enough to feed the reg board.

An externally hosted image should be here but it was not working when we last tested it.

This is the way my secondaries are wired.

An externally hosted image should be here but it was not working when we last tested it.


This is the PSU I made on a breadboard.
R1 and R2 are 0R22 5W

The Coleman Reg R20=1K, Reg R1=0R82 5W
The Dummy res connected to reg output is 3R1 20W (10R 10W + 4R7 10W) that was all I had on hand to mimic a 300B.

The PSU gives 14.423V DC unloaded, so fine.

But as soon as I wire the reg board The Psu outputs 5.185V DC ??

Regboard output (with 3.1ohm dummy resistor) gives 2.71V DC
0.856A between PSU + output and regboard + input

the output does not seem to change much by altering the RV1 pot on the regboard.

Something is not working fine here. Rod asked to invert the phase of one of my secondaries, but I don't really know how to do this in my configuration.

Any clues?
 
Last edited:
E

euro21

Member
Joined 2004
Paid Member
Test 5+5V (4A) AC without raw DC supply.
Measure it first unloaded, then loaded with 2A.

If it is OK, test raw DC supply.
Measure it first unloaded, then loaded with 2A.

IF it is OK, test R.C. regulator.

BTW this PSU is for only ONE 300B. Do you have two power transformer?
 
C

cowneko

Member
Joined 2013
Shall I use a pure resistive load to test the secondary under 2A load? like direct wiring a 4R7 10W (witch shall draw 2A from 10V 4A) across the 5V secondary.

BTW this PSU is for only ONE 300B. Do you have two power transformer?
Click to expand...
Of course I'll get a second PT for the second block.

I have used about a half dozen pairs of Rod's filament regulators and haven't had any problems with them. A couple of them have been running since November of 2011
Click to expand...

I'm pretty sure the regboards are fine, the problem surely lies somewhere else.
 
E

euro21

Member
Joined 2004
Paid Member
Chinese "4A". :)
Try to use "real" 9V filament transformer.
 

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E

euro21

Member
Joined 2004
Paid Member
A little underrated.
If you waste 16VA for one filament power, the filament transformer would be at least 32VA. The common (shared primary, individual secondaries) transformer below 64VA will be warm.

This transformer is good, if you use CT secondary and two diodes instead of graetz.

If you want to use graetz, this is better:
TS40/026 INDEL - Transformateur: de reseau | TME - Composants electroniques
 
Ketje

Ketje

Member
Joined 2012
cowneko said:
I get 6,26V AC with a 4R7 res on the secondary, that means 1,33A....
Click to expand...
You have two 5volts/4A in series, good for 10Vvolts 4Amp.
Even for a bad transformer 6,3volts at only 1,33A is not normal.
There is something else going on :confused:
An other thing, with the Cole regulator and an output of 10volt, 12volt in isn't enough.I think at least 15volt, that means a transformer with 12volt AC.
Mona
 
andyjevans

andyjevans

Member
Joined 2003
artsandmedia.com
Ketje said:
An other thing, with the Cole regulator and an output of 10volt, 12volt in isn't enough.I think at least 15volt, that means a transformer with 12volt AC.
Mona
Click to expand...

Yes indeed. The Ver. 7 requires less headroom than previous versions which were good at around 6v-7v headroom but even so, I'd suggest 5v. Rod will tell you.

Why not choke input? I'd be doing that with a big chunky 18v transformer without much voltage drop.
 
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