Parmeko P.M.A Mark 2 transformer help needed. - UK Vintage Radio Repair and Restoration Discussion Forum

Bomber county · 29th Nov 2018, 1:31 pm

Trying to gather bits together to build a power supply for an R1155. Saved this transformer out of an old valve based oscilloscope as logically thinking it ought to have the correct voltages in there somewhere for the heaters and HT. Can't find any info online or a schematic for the scope and probing around with a meter isn't getting me anywhere....Scope was an old Solartron 1400 (did work recently but nobody wanted it). Other than Parmeko PMA Mk2, Parm 51 and 301060170 there isn't anything else to identify the transformer.

Inputs are not an issue as it is "as removed" complete with the input voltage selector panel and mains lead still attached. There are 16 output terminals on the top, i have tried probing adjacent pairs and opposite pairs but not really seen anything sensible (don't seem to have 6.3v anywhere). They are numbered but don't really follow a logical pattern.

ms660 · 29th Nov 2018, 2:06 pm

So far as I can make out:

11-12=155v
13-14=46v
15-16-17=0v-100v-1,000v
18-19=6.3v@3.5 amps
20-21-22=14v-0v-14v
23-24=6.3v@2.5 amps
25-26=6.3v(CRT Heater?)

The above from the CD1400 manual at Elektrotanya

Lawrence.

Bomber county · 29th Nov 2018, 2:53 pm

Thanks for that, sussed it now. After some head scratching I found the neutral had been snipped off...Doesn't seem it will be any good for my R1155 though which is frustrating. Oh well the search continues.

buggies · 29th Nov 2018, 9:10 pm

Just to add that the 155 volt winding fed a 2 diode voltage doubler to provide 360 volt HT(320v decoupled) at about 240mA.
A negative 56 volt rail could provide 170mA and the -16 volt rail 330mA.
Total consumption up to 200VA.
And a large thump when switching on at wrong part of cycle...

Diabolical Artificer · 30th Nov 2018, 7:23 am

Scope tfmr's often have dual primaries at least, so need jumpering. You're not too far away so your welcome to rumage through my tfmr stash if it helps or if it comes to it borrow my coil winder and wind your own.

Andy.

29th Nov 2018, 1:31 pm	#1
Bomber county Pentode Join Date: Oct 2009 Location: Holbeach, Lincolnshire, UK. Posts: 134	Parmeko P.M.A Mark 2 transformer help needed. Trying to gather bits together to build a power supply for an R1155. Saved this transformer out of an old valve based oscilloscope as logically thinking it ought to have the correct voltages in there somewhere for the heaters and HT. Can't find any info online or a schematic for the scope and probing around with a meter isn't getting me anywhere....Scope was an old Solartron 1400 (did work recently but nobody wanted it). Other than Parmeko PMA Mk2, Parm 51 and 301060170 there isn't anything else to identify the transformer. Inputs are not an issue as it is "as removed" complete with the input voltage selector panel and mains lead still attached. There are 16 output terminals on the top, i have tried probing adjacent pairs and opposite pairs but not really seen anything sensible (don't seem to have 6.3v anywhere). They are numbered but don't really follow a logical pattern. Attached Thumbnails

29th Nov 2018, 2:06 pm	#2
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Parmeko P.M.A Mark 2 transformer help needed. So far as I can make out: 11-12=155v 13-14=46v 15-16-17=0v-100v-1,000v 18-19=6.3v@3.5 amps 20-21-22=14v-0v-14v 23-24=6.3v@2.5 amps 25-26=6.3v(CRT Heater?) The above from the CD1400 manual at Elektrotanya Lawrence.

29th Nov 2018, 2:53 pm	#3
Bomber county Pentode Join Date: Oct 2009 Location: Holbeach, Lincolnshire, UK. Posts: 134	Re: Parmeko P.M.A Mark 2 transformer help needed. Thanks for that, sussed it now. After some head scratching I found the neutral had been snipped off...Doesn't seem it will be any good for my R1155 though which is frustrating. Oh well the search continues.

29th Nov 2018, 9:10 pm	#4
buggies Heptode Join Date: Jan 2009 Location: West Lothian, UK. Posts: 761	Re: Parmeko P.M.A Mark 2 transformer help needed. Just to add that the 155 volt winding fed a 2 diode voltage doubler to provide 360 volt HT(320v decoupled) at about 240mA. A negative 56 volt rail could provide 170mA and the -16 volt rail 330mA. Total consumption up to 200VA. And a large thump when switching on at wrong part of cycle... __________________ George

30th Nov 2018, 7:23 am	#5
Diabolical Artificer Dekatron Join Date: Jul 2009 Location: Sleaford, Lincs. UK. Posts: 7,662	Re: Parmeko P.M.A Mark 2 transformer help needed. Scope tfmr's often have dual primaries at least, so need jumpering. You're not too far away so your welcome to rumage through my tfmr stash if it helps or if it comes to it borrow my coil winder and wind your own. Andy. __________________ Curiosity hasn't killed this cat...so far.