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Kolster-Brandes LR10 restoration.

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Boingy
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Hello all,

I recently bought a KB LR10 portable radio from a charity that aids an hospice in Huddersfield with the aim of restoring it. The charity kindly removed the valves and knobs for me and sent it on its way.

The LR10 is a basic "4+1" valve arrangement that hails from 1954.

Many thanks to Chris for supplying me the Trader sheet and service manual for this model.

Here's a couple of pictures of the cabinet and chassis.

Front as found
Chassis left
Valves and knobs
Chassis right

Chassis out

Chassis out

Next, had a look at the valves. V4 is cooked, by looks. V5 is stressed and an EZ80 instead of a 6X5GT.

V4 and V5

Looking under the chassis revealed several waxies, some split Hunts caps and a reservoir cap that has spilled its electrolyte out.

Under mid chassis
Under chassis right
Leaking reservoir

Looks like there's a bit of work to do electronically, so I cleaned up the cabinet a little, just as a starter.

Front after cleanup

The next thing would be to try and source V4 (6AQ5), V5 (6X5GT) and the 32+32uf@350V.

Any advice or help would be appreciated 🙂

All the best,

Tony

Standards are like toothbrushes. Everybody needs them, but nobody want to use yours!

 
Posted : 20/05/2018 3:19 pm
Cathovisor
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Two things, Tony:

  1. A 6X5GT is an octal valve. KB would modify their sets as time went by, this is one of them so the EZ80 is original. The FB10 "Toaster" had three valve changes during its production run!
  2. Before condemning the 6AQ5, I'd try it. These valves always look a bit stressed.

I have an earlier version, an HR10. It is a cracking set, well worth the attention.

 
Posted : 20/05/2018 3:42 pm
PYE625
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Hi Tony, well I'm willing to bet the valves will be fine as they look normal for ones that are used, plus it looks like the valve holder for the rectifier could have been a factory fit and it is a Brimar EZ80 too. Don't write off the electrolytic just yet, it may after a clean-up be ok when reformed. Then again, it may not.  ? 

Oops crossed post's with Catho.

To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 20/05/2018 3:45 pm
Cathovisor
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Quite - the FB10 always had the same three signal valves but the output and rectifier valves progressively changed from a 6V6GT and a 6X5GT to a 6BW6 and 6X4 - with the output valve changing first. It looks to be a factory-fit 'special' valveholder for the EZ80 in Tony's set.

 
Posted : 20/05/2018 4:04 pm
sideband
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Yes be careful. As explained above manufacturers sometimes changed valve types during production. KB probably did this more than anyone else. The EZ80 fitted will most likely be original (but not necessarily the one shown on the circuit). As mentioned, the 6X5 (also known as EZ35) is an octal so if you'd bought one of those.....it wouldn't fit!! It would pay you to get familiar with some of the common valve types and their bases. I would suggest you try and find a valve equivalents book or use the National Valve Museum http://www.r-type.org/ as a reference. The valves look fine....you can't really tell just by looking (unless it's gassed). The 6AQ5 (which I think is the same as a Mullard EL90) has an internal coating so that blacking is completely normal.

So hold fire on the valves and carry on with the rest of the restoration. You'll soon know if any of the valves are dud.

 
Posted : 20/05/2018 4:32 pm
Boingy
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Thank you all for your wise words.

I didn't know that KB would modify quite so much during the production run. There again, everybody does it!

The internal coating of the output valve is a new one on me, but every day is a school day. Would I be correct in guessing that the coating is there to dissipate heat?

I Will clean up the reservoir cap and give a go on that reformer I recently made.

Once again, thank you for your help so far. I look forward to learning more as I progress with the repair.

All the best,

Tony

Standards are like toothbrushes. Everybody needs them, but nobody want to use yours!

 
Posted : 20/05/2018 6:28 pm
Boingy
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Oops, the reply posted twice.... Sorry!

Standards are like toothbrushes. Everybody needs them, but nobody want to use yours!

 
Posted : 20/05/2018 6:29 pm
Cathovisor
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I have to say that it would be a considerable surprise if that electrolytic reforms, given that it appears to have vented a fair bit of electrolyte. 

Yes, the coating inside the 6AQ5 is there to help it dissipate heat. 

 
Posted : 20/05/2018 6:45 pm
PYE625
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Posted by: Cathovisor

I have to say that it would be a considerable surprise if that electrolytic reforms, given that it appears to have vented a fair bit of electrolyte. 

Me too if I was honest. I think both anodes of the rectifier are connected in parallel, so a half-wave only is smoothed.

To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 20/05/2018 6:49 pm
crustytv
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Hi Tony,

Nice looking set you've got yourself there.

I have an RS 32+32 uF 400V in stock ( higher voltage as I'm sure you are aware is perfectly fine). Its yours FOC just pm me your address and I'll get it sent off. 

I would offer to reform it for you but I'm sure you'e itching to use your new Carlos Fandango reformer.  ? 

3232

p.s. 

I have a number of NOS RCA 6AQ5A in stock, these are identical to the 6AQ5 (see data sheet under components in the Data Library). Your welcome to one of those too, however like the guys have already said, I would hardly condemn the bottles at this stage just on visuals alone. Glassware in valve sets are the least likely components to fail. In the 10 years I've been dabbling in Radio & TV I've only replaced about 6 and they had physical faults ( down to air, shorted etc) which sort of makes a mockery of me collecting almost 5,000 valves. I've some right raga-muffin line-output valves operating in some sets you would condemn if you saw them and as for the PFL200 luminance in the 700 series sets, well they looked nuked but still work perfectly fine. You have to admire valves, they are so robust taking a lot of abuse.

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Posted : 20/05/2018 7:20 pm
Nuvistor
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If you are stuck for the valves Langrex have 600 6AQ5 and 4000 6X5Gt in stock.

See how the ones you have behave and Chris has a 6AQ5A.

 

 

Frank

 
Posted : 20/05/2018 7:33 pm
Cathovisor
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But we've determined that Tony doesn't need, and never did need a 6X5GT, Frank. 

 
Posted : 20/05/2018 7:48 pm
Cathovisor
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Posted by: PYE625

Me too if I was honest. I think both anodes of the rectifier are connected in parallel, so a half-wave only is smoothed.

Yeah, Bush used to pull that stunt too in some of their sets - especially the export ones. But the original issue of the LR10 manual from the KB Museum site shows a conventional full-wave rectifier circuit.
 

 
Posted : 20/05/2018 8:10 pm
Nuvistor
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Posted by: Cathovisor

But we've determined that Tony doesn't need, and never did need a 6X5GT, Frank. 

Ah, yes, I will go and stand in the corner now, my fault trying to catchup with all the recent posts and missing vital info.

Frank

 
Posted : 20/05/2018 8:12 pm
Cathovisor
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Don't worry Frank, I've just been well and truly shot down in flames for not reading a post thoroughly on another forum - before I kicked off at the OP... ? 

 
Posted : 20/05/2018 8:16 pm
PYE625
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I think the electrolytic fitted here is a slim type with chassis lugs as opposed to the clip arrangement. It could make direct replacement tricky, unless the right type is available of course.

To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 20/05/2018 8:34 pm
Cathovisor
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Posted by: PYE625

I think the electrolytic fitted here is a slim type with chassis lugs as opposed to the clip arrangement. It could make direct replacement tricky, unless the right type is available of course.

The so-called "twist-lock" package.

 
Posted : 20/05/2018 8:39 pm
Katie Bush
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I have a couple of Murphys, 674 and 684, with those twist lock smoothers - Like Tony's, one of mine has well and truly barfed, but it does still do its job! Amazing really, but I'd advocate in favour of replacing (or re-stuffing) if one of those options is available.

 
Posted : 20/05/2018 9:06 pm
sideband
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Posted by: Cathovisor

Yes, the coating inside the 6AQ5 is there to help it dissipate heat. 

The reason this is done is because it's an output valve on a B7G base....there is a lot of valve with only a relatively small envelope. Some manufacturers (HMV come to mind) fitted black screening cans over  the output and rectifier valves (B7G bases) to help them dissipate the heat and lengthen the valve life. It must have worked because my HMV is nearly 60 years old with the original rectifier and output still fitted.

It wasn't so important with B9A and certainly not with octal valves since the larger glass envelope dissipated the heat better.

 

 
Posted : 20/05/2018 9:51 pm
Cathovisor
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Try the ECLL800 Rich... two output valves and their phase splitter in one envelope - in a B9A base.

 
Posted : 20/05/2018 9:53 pm
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