Taylor 65B Transformer to Rectifier Wiring Doesn't Make Sense - UK Vintage Radio Repair and Restoration Discussion Forum

LittleDuckAlex · 19th Nov 2014, 8:14 pm

Hey everyone,

I'm trying to test the mains transformer in my Taylor 65B signal generator. I went to test the secondary HT winding at pins 3 and 5 (the anodes) of the 6X5 rectifier. However, I couldn't progress because although the diagram in the manual shows everything wired as you'd expect, in the set, pins 3 and 5 are wired together. There are five wires making up the secondary; there's the heater wire and one side of the HT winding, then the rest all go to ground. I've attached a drawing of how it appears to be wired.

Question is, am I being stupid, or is there no way that this can work? I just can't make any sense of it. It looks untouched, and in other pictures of 65Bs I can only see two wires leading to the 6X5 base. Can someone explain what's going on?

Thanks,
Alex

AC/HL · 19th Nov 2014, 8:56 pm

It looks to have been got at, the rectifier could be strapped for half-wave working, but the transformer would object to being short circuited!

PS. Circuit courtesy of the valvepage.

LittleDuckAlex · 19th Nov 2014, 10:18 pm

Things really don't look good. I have no continuity between pin 3 and the three ground wires. Looks like the HT winding is completely burned out. I've read that 6X5 rectifiers have a bad reputation for shorting and burning out transformers. This one is an early 6X5GT, with the anodes arranged vertically. I'm wondering if the rectifier had a short, breaking the mains transformer, so the owner at the time made changes to make it run differently, but now it's completely died. Perhaps not though, as unless the owner retied all the valves back to their bases, I'd say these valves haven't ever been changed. Either way, I'm not too sure what I plan to do now. I would love to get it working again, but is it going to be worth me forking out for a new transformer?

AC/HL · 20th Nov 2014, 2:23 am

Does the 6X5GT heater warm up?
Disconnect the three HT secondary wires from the transformer and measure the voltages.
You should get the same from the centre-tap to either end.

avocollector · 20th Nov 2014, 4:05 am

Agree - from what I see of your diagram the transformer winding would burn out as the secondary is partially shorted. I would expect the two sides of the winding with the earthed centre tap to go to one of each two valve anodes as per the circuit diagram pdf above - unless they have cunningly disconnected the centre tap!

ukcol · 20th Nov 2014, 10:52 am

Quote:

Originally Posted by AC/HL

Circuit courtesy of the valvepage.

The thumbnail below comes from the above pdf.

TrevorG3VLF · 20th Nov 2014, 11:24 am

Ey oop me duck
If half the HT winding is OK, then a bridge rectifier on the good half can restore operation.
The bridge rectifier could consist of two diodes (1N4007) and the 6X5.

LittleDuckAlex · 22nd Nov 2014, 4:08 pm

Got around to looking at it a bit more. I disconnected and separated the earthed wires, then tested them. Nothing. The transformer's toast. I also tested the 6X5; it has no shorts and does alright for emissions.

Eddy_Stone · 22nd Nov 2014, 4:45 pm

Your drawing of how it appears to be wired must be incorrect. You show the secondary with two grounds on the same winding, this would look like short circuit on the transformer secondary and would blow the input fuse or toast the transformer

LittleDuckAlex · 22nd Nov 2014, 5:26 pm

There were 5 wires from the secondary, one heater wire connected to the rectifier base, one anode wire connected to the rectifier base, the other half of the heater winding connected to a grounding lug fastened to the back of the dial, and the other two connected to that same grounding lug. Those have to be one side of the HT winding, and it's tap.

If my drawing is incorrect, my description isn't. Although I believe my drawing is correct. If applying power in that state would cause the transformer to burn out, then that would explain why the transformer is burnt out.

Eddy_Stone · 22nd Nov 2014, 5:40 pm

OK I presume you just bought the signal Generator and it has not worked since you got it

LittleDuckAlex · 22nd Nov 2014, 6:26 pm

That is correct.

Harry40 · 22nd Nov 2014, 11:54 pm

You could probably get away with it if there is physically enough room to fit a small cheepo mains tranny. Just big enough to supply the HT. You would still need the existing tranny as the left hand windings are part of the modulation circuitry.
These windings have the HT going through them to energise and "modulate" the oscillator. hopefully the heater circuit still works and if the damaged windings are O/C and not short then the tranny should survive with just the two HT feeds disconnecting. That double tapped oscillator winding will be hard to duplicate if the whole of the tranny is unserviceable..

LittleDuckAlex · 23rd Nov 2014, 11:00 am

Quote:

Originally Posted by Harry40

You would still need the existing tranny as the left hand windings are part of the modulation circuitry.

Those windings are separate to the mains transformer, and are in the small transformer shown in the attached image. Thankfully that tests out good. I'm just going to need to find a suitable mains transformer.

Harry40 · 23rd Nov 2014, 2:28 pm

A separate tranny should work fine. Would you still use a valve or solid state rectifiers. I suppose feeding the oscillators it would need to be as clean as possible.

LittleDuckAlex · 23rd Nov 2014, 3:30 pm

I'd prefer to keep a valve rectifier. If I decide to stick to 6X5s, I'll use the later type.

ms660 · 23rd Nov 2014, 3:32 pm

According to this write up the mains transformer secondary is 110v-0v-110v.

http://www.radiomuseum.org/forum/tay...storation.html

Maybe someone could confirm.

Lawrence.

LittleDuckAlex · 23rd Nov 2014, 3:57 pm

Thanks Lawrence. I didn't think it'd be that low, so some confirmation would be nice. I have some information I've gathered on the component values but I don't think I've seen some of the ones mentioned in that post.

ms660 · 23rd Nov 2014, 4:04 pm

I couldn't say what is written in that link is correct or not, it was the only link that came up when I searched for Taylor 65b transformer.

Not sure how electrically similar it is but according to a manual annotation for the Taylor 66a (BAMA mirror site) the voltage across the reservoir capacitor is given as 215 vdc.

Lawrence.

gezza123 · 23rd Nov 2014, 10:05 pm

HI Alex,
I was very intrigued about your circuit so just had a look at mine, and would you believe it is the same as your first posted circuit. there are quite a few circuits on the net that use this sort of configuration.
There are no wires snipped on my generator and the connections are as my pic,
so here is my circuit that has worked for the past 20 odd years and no problems, so saying that I dont know if mine is right or wrong.

P;S there are three wires going to chassis, two black and one Red/Blk so it may be that they are only using one 150v output if that is correct then the transformer is 150v-0-150v. and I have been running mine on low voltage but it is very accurate.

Hope this helps good luck Gezza123.

19th Nov 2014, 8:14 pm	#1
LittleDuckAlex Retired Dormant Member Join Date: Jan 2014 Location: Sheffield, South Yorkshire, UK. Posts: 15	Taylor 65B Transformer to Rectifier Wiring Doesn't Make Sense Hey everyone, I'm trying to test the mains transformer in my Taylor 65B signal generator. I went to test the secondary HT winding at pins 3 and 5 (the anodes) of the 6X5 rectifier. However, I couldn't progress because although the diagram in the manual shows everything wired as you'd expect, in the set, pins 3 and 5 are wired together. There are five wires making up the secondary; there's the heater wire and one side of the HT winding, then the rest all go to ground. I've attached a drawing of how it appears to be wired. Question is, am I being stupid, or is there no way that this can work? I just can't make any sense of it. It looks untouched, and in other pictures of 65Bs I can only see two wires leading to the 6X5 base. Can someone explain what's going on? Thanks, Alex Attached Thumbnails

19th Nov 2014, 10:18 pm	#3
LittleDuckAlex Retired Dormant Member Join Date: Jan 2014 Location: Sheffield, South Yorkshire, UK. Posts: 15	Re: Taylor 65B Transformer to Rectifier Wiring Doesn't Make Sense Things really don't look good. I have no continuity between pin 3 and the three ground wires. Looks like the HT winding is completely burned out. I've read that 6X5 rectifiers have a bad reputation for shorting and burning out transformers. This one is an early 6X5GT, with the anodes arranged vertically. I'm wondering if the rectifier had a short, breaking the mains transformer, so the owner at the time made changes to make it run differently, but now it's completely died. Perhaps not though, as unless the owner retied all the valves back to their bases, I'd say these valves haven't ever been changed. Either way, I'm not too sure what I plan to do now. I would love to get it working again, but is it going to be worth me forking out for a new transformer?

20th Nov 2014, 2:23 am	#4
AC/HL Dekatron Join Date: Nov 2003 Location: Heckmondwike, West Yorkshire, UK. Posts: 9,642	Re: Taylor 65B Transformer to Rectifier Wiring Doesn't Make Sense Does the 6X5GT heater warm up? Disconnect the three HT secondary wires from the transformer and measure the voltages. You should get the same from the centre-tap to either end.

20th Nov 2014, 4:05 am	#5
avocollector Heptode Join Date: Jul 2010 Location: Wellington, New Zealand. Posts: 653	Re: Taylor 65B Transformer to Rectifier Wiring Doesn't Make Sense Agree - from what I see of your diagram the transformer winding would burn out as the secondary is partially shorted. I would expect the two sides of the winding with the earthed centre tap to go to one of each two valve anodes as per the circuit diagram pdf above - unless they have cunningly disconnected the centre tap!

20th Nov 2014, 11:24 am	#7
TrevorG3VLF Rest in Peace Join Date: Apr 2011 Location: Matlock, Derbyshire, UK. Posts: 1,378	Re: Taylor 65B Transformer to Rectifier Wiring Doesn't Make Sense Ey oop me duck If half the HT winding is OK, then a bridge rectifier on the good half can restore operation. The bridge rectifier could consist of two diodes (1N4007) and the 6X5.

22nd Nov 2014, 4:08 pm	#8
LittleDuckAlex Retired Dormant Member Join Date: Jan 2014 Location: Sheffield, South Yorkshire, UK. Posts: 15	Re: Taylor 65B Transformer to Rectifier Wiring Doesn't Make Sense Got around to looking at it a bit more. I disconnected and separated the earthed wires, then tested them. Nothing. The transformer's toast. I also tested the 6X5; it has no shorts and does alright for emissions.

22nd Nov 2014, 4:45 pm	#9
Eddy_Stone Retired Dormant Member Join Date: Jun 2014 Location: Boston, Massachusetts, USA Posts: 32	Re: Taylor 65B Transformer to Rectifier Wiring Doesn't Make Sense Your drawing of how it appears to be wired must be incorrect. You show the secondary with two grounds on the same winding, this would look like short circuit on the transformer secondary and would blow the input fuse or toast the transformer

22nd Nov 2014, 5:26 pm	#10
LittleDuckAlex Retired Dormant Member Join Date: Jan 2014 Location: Sheffield, South Yorkshire, UK. Posts: 15	Re: Taylor 65B Transformer to Rectifier Wiring Doesn't Make Sense There were 5 wires from the secondary, one heater wire connected to the rectifier base, one anode wire connected to the rectifier base, the other half of the heater winding connected to a grounding lug fastened to the back of the dial, and the other two connected to that same grounding lug. Those have to be one side of the HT winding, and it's tap. If my drawing is incorrect, my description isn't. Although I believe my drawing is correct. If applying power in that state would cause the transformer to burn out, then that would explain why the transformer is burnt out.

22nd Nov 2014, 5:40 pm	#11
Eddy_Stone Retired Dormant Member Join Date: Jun 2014 Location: Boston, Massachusetts, USA Posts: 32	Re: Taylor 65B Transformer to Rectifier Wiring Doesn't Make Sense OK I presume you just bought the signal Generator and it has not worked since you got it

22nd Nov 2014, 6:26 pm	#12
LittleDuckAlex Retired Dormant Member Join Date: Jan 2014 Location: Sheffield, South Yorkshire, UK. Posts: 15	Re: Taylor 65B Transformer to Rectifier Wiring Doesn't Make Sense That is correct.

22nd Nov 2014, 11:54 pm	#13
Harry40 Retired Dormant Member Join Date: Oct 2007 Location: Plymouth, Devon, UK. Posts: 51	Re: Taylor 65B Transformer to Rectifier Wiring Doesn't Make Sense You could probably get away with it if there is physically enough room to fit a small cheepo mains tranny. Just big enough to supply the HT. You would still need the existing tranny as the left hand windings are part of the modulation circuitry. These windings have the HT going through them to energise and "modulate" the oscillator. hopefully the heater circuit still works and if the damaged windings are O/C and not short then the tranny should survive with just the two HT feeds disconnecting. That double tapped oscillator winding will be hard to duplicate if the whole of the tranny is unserviceable..

23rd Nov 2014, 2:28 pm	#15
Harry40 Retired Dormant Member Join Date: Oct 2007 Location: Plymouth, Devon, UK. Posts: 51	Re: Taylor 65B Transformer to Rectifier Wiring Doesn't Make Sense A separate tranny should work fine. Would you still use a valve or solid state rectifiers. I suppose feeding the oscillators it would need to be as clean as possible.

23rd Nov 2014, 3:30 pm	#16
LittleDuckAlex Retired Dormant Member Join Date: Jan 2014 Location: Sheffield, South Yorkshire, UK. Posts: 15	Re: Taylor 65B Transformer to Rectifier Wiring Doesn't Make Sense I'd prefer to keep a valve rectifier. If I decide to stick to 6X5s, I'll use the later type.

23rd Nov 2014, 3:32 pm	#17
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Taylor 65B Transformer to Rectifier Wiring Doesn't Make Sense According to this write up the mains transformer secondary is 110v-0v-110v. http://www.radiomuseum.org/forum/tay...storation.html Maybe someone could confirm. Lawrence.

23rd Nov 2014, 3:57 pm	#18
LittleDuckAlex Retired Dormant Member Join Date: Jan 2014 Location: Sheffield, South Yorkshire, UK. Posts: 15	Re: Taylor 65B Transformer to Rectifier Wiring Doesn't Make Sense Thanks Lawrence. I didn't think it'd be that low, so some confirmation would be nice. I have some information I've gathered on the component values but I don't think I've seen some of the ones mentioned in that post.

23rd Nov 2014, 4:04 pm	#19
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Taylor 65B Transformer to Rectifier Wiring Doesn't Make Sense I couldn't say what is written in that link is correct or not, it was the only link that came up when I searched for Taylor 65b transformer. Not sure how electrically similar it is but according to a manual annotation for the Taylor 66a (BAMA mirror site) the voltage across the reservoir capacitor is given as 215 vdc. Lawrence.

23rd Nov 2014, 10:05 pm	#20
gezza123 Heptode Join Date: Mar 2010 Location: Eastham, Wirral, Merseyside, UK. Posts: 788	Re: Taylor 65B Transformer to Rectifier Wiring Doesn't Make Sense HI Alex, I was very intrigued about your circuit so just had a look at mine, and would you believe it is the same as your first posted circuit. there are quite a few circuits on the net that use this sort of configuration. There are no wires snipped on my generator and the connections are as my pic, so here is my circuit that has worked for the past 20 odd years and no problems, so saying that I dont know if mine is right or wrong. P;S there are three wires going to chassis, two black and one Red/Blk so it may be that they are only using one 150v output if that is correct then the transformer is 150v-0-150v. and I have been running mine on low voltage but it is very accurate. Hope this helps good luck Gezza123. Attached Thumbnails