Barker 88 - UK Vintage Radio Repair and Restoration Discussion Forum

rockinmark · 2nd Apr 2020, 11:19 pm

Would anyone have or be able to take a photo of the underside of the chassis of a Barkers 88.
I've downloaded the schematic and I seem to have an extra wax capacitor but can't find it.

Mark

AC/HL · 3rd Apr 2020, 12:10 am

Does this help: https://vintage-radio.net/forum/show...4&postcount=11

rockinmark · 3rd Apr 2020, 9:06 am

Thanks for that bill just found out that there is 2 sets of the same model 88 a early one and a late one. The one I need is a early one. The schematic I have is the trader service sheet. Sheet says there are 6 x 0.02uf capacitors but I've got 7. Judging by the mains colours I would say somebody has been in there.

Station X · 3rd Apr 2020, 10:07 am

Someone's definitely been in there as the smoothing caps have been replaced.

Where is the extra capacitor wired into the circuit? If it's the one you're pointing to, one end appears to go to chassis and the other to a pin on a valve holder. Which valve and which pin?

rockinmark · 3rd Apr 2020, 11:15 am

One end is on valve 2 and chassis the other end goes to a tag and then goes to r2, then to valve2 via r10 I think and green cable goes to magic eye

ms660 · 3rd Apr 2020, 11:30 am

C8 ?

Lawrence.

Station X · 3rd Apr 2020, 11:45 am

Agreed.

rockinmark · 3rd Apr 2020, 11:53 am

Ok if that's C8 then it would look at a glance I have a extra one here somewhere.

ms660 · 3rd Apr 2020, 12:21 pm

Quote:

Originally Posted by rockinmark

Ok if that's C8 then it would look at a glance I have a extra one here somewhere.

Looking at that photo your receiver appears to have the modified output stage, the details of which are given in the Trader sheet....in the text (end of center column) C31 is written as C91 (0.02uf)

Lawrence.

rockinmark · 3rd Apr 2020, 1:50 pm

Thanks for that Lawrence me not reading probably. why would they do a alternative output stage? I was given this set ages ago wasn't planning on doing it up as I think the output transformer has gone the person I got it from said he had it on all the time the one it stopped working that's about a year ago. But isolation has changed that so I thought let's have a quick look at it. I have a output transformer that is not to far off so could use that

Mark

Station X · 3rd Apr 2020, 1:57 pm

You say you think the output transformer has "gone". Have you tested it? Wound components are one of the first things to check when restoring a radio.

coopzone · 3rd Apr 2020, 2:21 pm

I've just been working on a barker 88 (about 2-3 weeks ago) my version was the modified output stage. This one had an extra 0.1 near the HT+ to ground by the output transformer connector. It was not on any of the circuits i could find.

My problem was that the one output valve had been forced in the holder and made t's own 'key' for the pin. I never noticed the first time i put it back together, and yes, got the valve wrong. It burned out the 100ohm g2 resistor. It was very smokey!

It's ok now, if you need any info i can probably get it on the bench next week some ime.

Derek

rockinmark · 3rd Apr 2020, 3:41 pm

Graham, yeah I did check the output transformer and not getting any ohms or continuity on the green so I was presuming it would need a replacement ,that's one of the reasons I left it, but as I have more time on my hands why not. I have got some with a primary of 470.0 ohms and a secondary 0.40ohms i thought it would do.
Thank you Derek i should be ok, but if I need me help I will let you know

Mark

Sideband · 3rd Apr 2020, 9:16 pm

I have a Barker 88 and so far have not found an exact circuit for it. Mine uses a 6J6 as a phase splitter....the circuit I have shows the 6Q7 being used as phase splitter. Extra components are used around the 6J6 so in the end I 'reverse engineered' the circuit.

Station X · 3rd Apr 2020, 9:50 pm

Quote:

Originally Posted by rockinmark

Graham, yeah I did check the output transformer and not getting any ohms or continuity on the green so I was presuming it would need a replacement ,that's one of the reasons I left it, but as I have more time on my hands why not. I have got some with a primary of 470.0 ohms and a secondary 0.40ohms i thought it would do.

Mark

This set has a push-pull output stage, so you'll need a suitable push-pull output transformer with a centre tapped primary.

The set also uses an energised speaker, so check the continuity of all the speaker windings.

rockinmark · 3rd Apr 2020, 10:25 pm

The speaker winding is ok I will take the speaker out in morning to have a better look at the transformer. Can you still get one like that Graham

rockinmark · 4th Apr 2020, 8:35 am

What could I use as a replacement I dont think rewinding would be worth the cost

Silicon · 4th Apr 2020, 8:55 am

If you want to hear some sound from this receiver you could use a mains transformer as a temporary audio output transformer.

You will need a transformer with a split primary (120 V + 120 V) and a 3 Volt output.

That should be a reasonable match for a 6V6 push pull output stage.

rockinmark · 14th Apr 2020, 3:39 pm

Hi what can I use to replace c13 its valve 3 cathode by-pass 25.0uf dont know the voltage is. Would this be a important one to change everything else I have from my stock but not sure about this one

Mark

coopzone · 14th Apr 2020, 3:51 pm

I would use something like 22uf at 25volt(or higher)

2nd Apr 2020, 11:19 pm	#1
rockinmark Heptode Join Date: Sep 2014 Location: St Albans, Hertfordshire, UK. Posts: 594	Barker 88 Would anyone have or be able to take a photo of the underside of the chassis of a Barkers 88. I've downloaded the schematic and I seem to have an extra wax capacitor but can't find it. Mark

3rd Apr 2020, 12:10 am	#2
AC/HL Dekatron Join Date: Nov 2003 Location: Heckmondwike, West Yorkshire, UK. Posts: 9,642	Re: Barker 88 Does this help: https://vintage-radio.net/forum/show...4&postcount=11

3rd Apr 2020, 9:06 am	#3
rockinmark Heptode Join Date: Sep 2014 Location: St Albans, Hertfordshire, UK. Posts: 594	Re: Barker 88 Thanks for that bill just found out that there is 2 sets of the same model 88 a early one and a late one. The one I need is a early one. The schematic I have is the trader service sheet. Sheet says there are 6 x 0.02uf capacitors but I've got 7. Judging by the mains colours I would say somebody has been in there. Attached Thumbnails

3rd Apr 2020, 10:07 am	#4
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: Barker 88 Someone's definitely been in there as the smoothing caps have been replaced. Where is the extra capacitor wired into the circuit? If it's the one you're pointing to, one end appears to go to chassis and the other to a pin on a valve holder. Which valve and which pin? __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

3rd Apr 2020, 11:15 am	#5
rockinmark Heptode Join Date: Sep 2014 Location: St Albans, Hertfordshire, UK. Posts: 594	Re: Barker 88 One end is on valve 2 and chassis the other end goes to a tag and then goes to r2, then to valve2 via r10 I think and green cable goes to magic eye Attached Thumbnails

3rd Apr 2020, 11:30 am	#6
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Barker 88 C8 ? Lawrence.

3rd Apr 2020, 11:45 am	#7
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: Barker 88 Agreed. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

3rd Apr 2020, 11:53 am	#8
rockinmark Heptode Join Date: Sep 2014 Location: St Albans, Hertfordshire, UK. Posts: 594	Re: Barker 88 Ok if that's C8 then it would look at a glance I have a extra one here somewhere. Attached Thumbnails

3rd Apr 2020, 1:50 pm	#10
rockinmark Heptode Join Date: Sep 2014 Location: St Albans, Hertfordshire, UK. Posts: 594	Re: Barker 88 Thanks for that Lawrence me not reading probably. why would they do a alternative output stage? I was given this set ages ago wasn't planning on doing it up as I think the output transformer has gone the person I got it from said he had it on all the time the one it stopped working that's about a year ago. But isolation has changed that so I thought let's have a quick look at it. I have a output transformer that is not to far off so could use that Mark

3rd Apr 2020, 1:57 pm	#11
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: Barker 88 You say you think the output transformer has "gone". Have you tested it? Wound components are one of the first things to check when restoring a radio. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

3rd Apr 2020, 2:21 pm	#12
coopzone Hexode Join Date: Jan 2018 Location: Cannock, Staffordshire, UK. Posts: 268	Re: Barker 88 I've just been working on a barker 88 (about 2-3 weeks ago) my version was the modified output stage. This one had an extra 0.1 near the HT+ to ground by the output transformer connector. It was not on any of the circuits i could find. My problem was that the one output valve had been forced in the holder and made t's own 'key' for the pin. I never noticed the first time i put it back together, and yes, got the valve wrong. It burned out the 100ohm g2 resistor. It was very smokey! It's ok now, if you need any info i can probably get it on the bench next week some ime. Derek

3rd Apr 2020, 3:41 pm	#13
rockinmark Heptode Join Date: Sep 2014 Location: St Albans, Hertfordshire, UK. Posts: 594	Re: Barker 88 Graham, yeah I did check the output transformer and not getting any ohms or continuity on the green so I was presuming it would need a replacement ,that's one of the reasons I left it, but as I have more time on my hands why not. I have got some with a primary of 470.0 ohms and a secondary 0.40ohms i thought it would do. Thank you Derek i should be ok, but if I need me help I will let you know Mark

3rd Apr 2020, 9:16 pm	#14
Sideband Dekatron Join Date: Oct 2003 Location: Croydon, Surrey, UK. Posts: 7,577	Re: Barker 88 I have a Barker 88 and so far have not found an exact circuit for it. Mine uses a 6J6 as a phase splitter....the circuit I have shows the 6Q7 being used as phase splitter. Extra components are used around the 6J6 so in the end I 'reverse engineered' the circuit. __________________ There are lots of brilliant keyboard players and then there is Rick Wakeman.....

3rd Apr 2020, 10:25 pm	#16
rockinmark Heptode Join Date: Sep 2014 Location: St Albans, Hertfordshire, UK. Posts: 594	Re: Barker 88 The speaker winding is ok I will take the speaker out in morning to have a better look at the transformer. Can you still get one like that Graham

4th Apr 2020, 8:35 am	#17
rockinmark Heptode Join Date: Sep 2014 Location: St Albans, Hertfordshire, UK. Posts: 594	Re: Barker 88 What could I use as a replacement I dont think rewinding would be worth the cost

4th Apr 2020, 8:55 am	#18
Silicon Nonode Join Date: Jun 2007 Location: Coulsdon, London, UK. Posts: 2,167	Re: Barker 88 If you want to hear some sound from this receiver you could use a mains transformer as a temporary audio output transformer. You will need a transformer with a split primary (120 V + 120 V) and a 3 Volt output. That should be a reasonable match for a 6V6 push pull output stage.

14th Apr 2020, 3:39 pm	#19
rockinmark Heptode Join Date: Sep 2014 Location: St Albans, Hertfordshire, UK. Posts: 594	Re: Barker 88 Hi what can I use to replace c13 its valve 3 cathode by-pass 25.0uf dont know the voltage is. Would this be a important one to change everything else I have from my stock but not sure about this one Mark Attached Thumbnails

14th Apr 2020, 3:51 pm	#20
coopzone Hexode Join Date: Jan 2018 Location: Cannock, Staffordshire, UK. Posts: 268	Re: Barker 88 I would use something like 22uf at 25volt(or higher)