sad AR88 owner - UK Vintage Radio Repair and Restoration Discussion Forum

cendoubleu · 3rd Feb 2007, 2:26 am

Hi Folks,
first post to the forum. Just acquired an AR88 in rather sad condition. It had languished in a (dry) garage for about 10 years, but prior to that been stored in an airing cupboard where the tank leaked! Anyway, I got the set for free as the guy wanted to clear out his garage. Being a bit naive, I plugged it in and hey presto all worked. Quite amazing. Well the jubilation last for a day then it died on me. The output valve, on removal, rattled a bit so I assumed that was the problem. This was replaced and off it went again for about 3 hours. I have since learnt from reading these forum pages and other vintage radio articles of the wisdom of checking grid capacitors and on this occasion output capacitors. Unfortunately it was too late and I have found tonight that the output transformer primary is kaput. I have also noticed some of the bath tub caps are leaking oil. So this has turned from a "get it up and running" job to more of a restoration. But its all good fun and stops me getting bored. It's also made me drag the valve theory I learnt over 30 years ago kicking and screaming from the depths of my brain. So now on the hunt for an o/p transformer.
Regards to all

Station X · 3rd Feb 2007, 9:10 am

Welcome to the forums.

There's some info on the AR88 here:-

https://www.vintage-radio.net/forum/...ead.php?t=2010

Failure of the output transformer is a common problem, often due to using the wrong impedance speaker or runing the transformer into an open circuit.

Output transformers were available from Colomor:-

http://www.websamba.com/colomor

Click on the first "here" link on the above page, then on "radio"

cendoubleu · 3rd Feb 2007, 10:50 am

thanks for the info Graham and apologies for posting to the wrong area.
I think the o/p transformer problem was probably down to a leaky plate capacitor on the o/p valve. Had I read all the available info prior to switch on I would have changed it but there we go. I have checked with Colomor but they don't have any at the moment but I shall keep looking. The bath tubs I shall change for modern components as I am not so much interested in having a faithful looking receiver, but in getting a once great receiver back into fully working order. I believe these things are like old cameras (another passion) they should be used not just look good.
I am sure there will be further posts along the way. From what I have read already, there is a huge amount of knowledge amongst the members of this site.

Station X · 3rd Feb 2007, 11:15 am

I originally replaced the bathtub capacitors in my AR88 with new capacitors mounted on custom made tag strips secured to the original mounting holes for the bathtubs. That was a lot of work and I would have been better off rebuilding the bathtubs. That's exactly what I later did,

Another possibility is to fit new capacitors directly on the valve pins.

The most tricky capacitors to change are those inside the screening cans.

Not good to know that Colomor have no output transformers, as I think they were the last remaining source for this item.

cendoubleu · 3rd Feb 2007, 11:57 am

If I can't find anything via Colomor/Ebay, I will resort to a substitute. I guess it shouldn't be too difficult to work out what is required, transforming a plate load resistance of 5.5K to 2.5 Ohms for the speaker (well 4 Ohms would do), along with the plate current value. The only tricky bit is the tapped secondary providing the f/b path to the previous stage.

dave walsh · 3rd Feb 2007, 4:04 pm

Please keep reporting on your progress. I've got one of these with the apparently classic u/s OPT so I'll be interested in how you get on. I'm also trying to co-ordinate all my written info on this set. I got mine from a forum member and it is badged as "Slave 34. " so I'm guessing that it was part of a war time listening station. Cheers Dave

cendoubleu · 3rd Feb 2007, 4:30 pm

Hi Dave, yes I will keep updating. I would imagine that I will probably have to take the substitute route as far as the transformer is concerned. On another site, someone has done just this using a "universal" transformer from RS but I can't seem to find one on the current RS site. I think in the meantime, I shall keep looking and also look for a nice s/w receiver for something to listen to!

cendoubleu · 3rd Feb 2007, 4:31 pm

I guess your Ar88 was part of a diversity setup.

dave walsh · 3rd Feb 2007, 6:27 pm

Perhaps someone will comment on your Diversity notion-VMARS people maybe? I won't be back at Base Camp in Lancs for a month or so but I will be having a look for OPT's. You never know-I might find more than one!
Cheers Dave

cendoubleu · 3rd Feb 2007, 8:33 pm

just found this: http://www.ampmaker.com/ot01x.asp which I reckon would do the job

3rd Feb 2007, 2:26 am	#1
cendoubleu Tetrode Join Date: Jan 2007 Location: Lincoln, Lincs. UK. Posts: 94	sad AR88 owner Hi Folks, first post to the forum. Just acquired an AR88 in rather sad condition. It had languished in a (dry) garage for about 10 years, but prior to that been stored in an airing cupboard where the tank leaked! Anyway, I got the set for free as the guy wanted to clear out his garage. Being a bit naive, I plugged it in and hey presto all worked. Quite amazing. Well the jubilation last for a day then it died on me. The output valve, on removal, rattled a bit so I assumed that was the problem. This was replaced and off it went again for about 3 hours. I have since learnt from reading these forum pages and other vintage radio articles of the wisdom of checking grid capacitors and on this occasion output capacitors. Unfortunately it was too late and I have found tonight that the output transformer primary is kaput. I have also noticed some of the bath tub caps are leaking oil. So this has turned from a "get it up and running" job to more of a restoration. But its all good fun and stops me getting bored. It's also made me drag the valve theory I learnt over 30 years ago kicking and screaming from the depths of my brain. So now on the hunt for an o/p transformer. Regards to all

3rd Feb 2007, 9:10 am	#2
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: sad AR88 owner Welcome to the forums. There's some info on the AR88 here:- https://www.vintage-radio.net/forum/...ead.php?t=2010 Failure of the output transformer is a common problem, often due to using the wrong impedance speaker or runing the transformer into an open circuit. Output transformers were available from Colomor:- http://www.websamba.com/colomor Click on the first "here" link on the above page, then on "radio" __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

3rd Feb 2007, 10:50 am	#3
cendoubleu Tetrode Join Date: Jan 2007 Location: Lincoln, Lincs. UK. Posts: 94	Re: sad AR88 owner thanks for the info Graham and apologies for posting to the wrong area. I think the o/p transformer problem was probably down to a leaky plate capacitor on the o/p valve. Had I read all the available info prior to switch on I would have changed it but there we go. I have checked with Colomor but they don't have any at the moment but I shall keep looking. The bath tubs I shall change for modern components as I am not so much interested in having a faithful looking receiver, but in getting a once great receiver back into fully working order. I believe these things are like old cameras (another passion) they should be used not just look good. I am sure there will be further posts along the way. From what I have read already, there is a huge amount of knowledge amongst the members of this site.

3rd Feb 2007, 11:15 am	#4
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: sad AR88 owner I originally replaced the bathtub capacitors in my AR88 with new capacitors mounted on custom made tag strips secured to the original mounting holes for the bathtubs. That was a lot of work and I would have been better off rebuilding the bathtubs. That's exactly what I later did, Another possibility is to fit new capacitors directly on the valve pins. The most tricky capacitors to change are those inside the screening cans. Not good to know that Colomor have no output transformers, as I think they were the last remaining source for this item. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

3rd Feb 2007, 11:57 am	#5
cendoubleu Tetrode Join Date: Jan 2007 Location: Lincoln, Lincs. UK. Posts: 94	Re: sad AR88 owner If I can't find anything via Colomor/Ebay, I will resort to a substitute. I guess it shouldn't be too difficult to work out what is required, transforming a plate load resistance of 5.5K to 2.5 Ohms for the speaker (well 4 Ohms would do), along with the plate current value. The only tricky bit is the tapped secondary providing the f/b path to the previous stage.

3rd Feb 2007, 4:04 pm	#6
dave walsh Dekatron Join Date: Jan 2006 Location: Ramsbottom (Nr Bury) Lancs or Bexhill (Nr Hastings) Sussex. Posts: 5,817	Re: sad AR88 owner Please keep reporting on your progress. I've got one of these with the apparently classic u/s OPT so I'll be interested in how you get on. I'm also trying to co-ordinate all my written info on this set. I got mine from a forum member and it is badged as "Slave 34. " so I'm guessing that it was part of a war time listening station. Cheers Dave

3rd Feb 2007, 4:30 pm	#7
cendoubleu Tetrode Join Date: Jan 2007 Location: Lincoln, Lincs. UK. Posts: 94	Re: sad AR88 owner Hi Dave, yes I will keep updating. I would imagine that I will probably have to take the substitute route as far as the transformer is concerned. On another site, someone has done just this using a "universal" transformer from RS but I can't seem to find one on the current RS site. I think in the meantime, I shall keep looking and also look for a nice s/w receiver for something to listen to!

3rd Feb 2007, 4:31 pm	#8
cendoubleu Tetrode Join Date: Jan 2007 Location: Lincoln, Lincs. UK. Posts: 94	Re: sad AR88 owner I guess your Ar88 was part of a diversity setup.

3rd Feb 2007, 6:27 pm	#9
dave walsh Dekatron Join Date: Jan 2006 Location: Ramsbottom (Nr Bury) Lancs or Bexhill (Nr Hastings) Sussex. Posts: 5,817	Re: sad AR88 owner Perhaps someone will comment on your Diversity notion-VMARS people maybe? I won't be back at Base Camp in Lancs for a month or so but I will be having a look for OPT's. You never know-I might find more than one! Cheers Dave

3rd Feb 2007, 8:33 pm	#10
cendoubleu Tetrode Join Date: Jan 2007 Location: Lincoln, Lincs. UK. Posts: 94	Re: sad AR88 owner just found this: http://www.ampmaker.com/ot01x.asp which I reckon would do the job