Barker Intermediate 88, another restoration job.

[boater sam]

Picked up a left handed Barker, believe it to be the intermediate model, all octal valves. There is a 6H6GT and a pair of KT61 output valves I have seen so far.

Left handed because the 4 knobs are to the left of the cabinet, the speaker grill on the right.  This one has the tuning eye on the left of the dial which signifies it is neither the early one else it would be on the right, nor the late one with miniature valves. All these models have different chassis.

I have not found a circuit diagram for it anywhere on line or in my Trader collection,  Can anyone supply a diagram please?

Its in fair condition, the cabinet is a cheap production made by J.B & Co of Slough, any known history?  
It has signs of damp, many of the glue blocks are loose in the bottom, and it has a small veneer lift on the top.  One broken knob, like none in any pictures I can find, being octagonal, light brown plastic without a skirt.

The capacitor can and clamp has gone and been replaced with five 8uf capacitors slung under the chassis. Otherwise it seems untouched.

A quick test shows it to be in working order, sort of, with deaf short wave and only 40 mV on the output valves grids.

It will restore well I think, need to find that knob or cast a new one, unless someone on here has one?

Picture when I have time..............

Sam.

[boater sam]

Had a better look at this set. 

Valve line up  ECH33 EF39 ( with all its red coating! ) 6H6GT 6SL7GT KT61 KT61 U50 & Y63 eye.
Not found any circuit diagram for this version  -  need some help there please.

So what have I got? The smoothing capacitor triple can has long gone. There are a total of six 8uf capacitors replacing it, 5 under and a double 8uf on top of the chassis. It works out as 24uf reservoir and two smoothing circuits with 16uf in each. There is a good hum so some or all these replacement capacitors are duff.

The eye is blind of course, but it would appear that all the valves are the originals. The pilot lamps work, one is a bayonet forced in instead of a mes bulb, nasty thing to do, its damaged the holder.

The tuning cord is cotton parcel string, however the wavechange flag indicator is correctly strung and working.

The cabinet has 8 loose corner glue block in the bottom, I have cleaned and reglued these. Not at all bad, everything else looks fair, the decoupling capacitors are Sprague cans, usually they are still serviceable.  The output grid coupling capacitors have already proved to be serviceable.

[Ed_Dinning]

Hi Sam, I had one like that many moons ago, but it used 6V6's instead of KT61's and was on 2 chassis, not one. the part most in need of repair was the case, but once done was a nice sounding set.

I believe it is described in Trader 747 (nov 1945)

Ed

[boater sam]

Hi Sam, I had one like that many moons ago, but it used 6V6's instead of KT61's and was on 2 chassis, not one. the part most in need of repair was the case, but once done was a nice sounding set.

I believe it is described in Trader 747  (nov 1945)

Ed

Hi Ed.
Not same set I'm afraid.
Trader 747 refers to the earlier set which is larger and not left handed. I believe that all these variants were made by different chassis makers.
There are at least 4 completely different valve line ups, this one uses a 6H6GT instead of a triode double diode for detector and AGC.
Though a bit cheap and cheerful cabinet wise,I like them.
Thanks for the reply.
Sam.

[boater sam]

One step forward, and one back.

Mains lead replaced, incorporating a mains earth on the chassis. I have no concerns about the mains transformer insulation being up to scratch, I want it earthed, if the transformer goes bad I will fix it. The QMB switch only breaks the live.

With new smoothers fitted, still got a 50Hz hum, Changes with volume. It ceases when the volume control is at maximum against the stop.
Its either picking up somewhere or its a valve heater cathode leak.  It will take a bit of detective work.

Found out why the shortwave is deaf, the oscillator coil core has broken in half at the end of the brass adjuster. I've removed the bits and epoxy glue seems to have repaired it. Will see tomorrow when its set and refitted.

The tuning gang has been restrung, therein lies an anomaly. Turning the tuning spindle produces bad crackles, but turning the gang capacitor by hand does not. Never found this before. I will try a bronze leaf spring on the end of the spindle under the chassis to ground it properly.
The oscillator tracking on medium and long is very good, station locations agree with the dial markings.

Extracted the bayonet bulb and fitted a proper 6.3V 0.3A MES one, seems a waste of time really as they don't light the dial very well at all.

[boater sam]

Not getting much feedback from others on the forum, but I carry on. Perhaps all are bored with my restorations?

Narrowed the mains hum  down to 50Hz pickup from the QMB mains switch on the back of the volume control. Switching the neutral instead of the line made no difference. Then I realised that the body of the control was not grounded, fitting a link wire to the chassis solved the hummmm. On inspection it seems that it is a replacement control, it must have hummed when it was first changed!

The shortwave oscillator core has set solid so refitted, and the set now picks up a few signals. It will need aligning. No idea what the frequency of the stations is or even what they are.

A new Y63 eye produces a good green glow but it is three quarters closed with no signal and only closes a bit more with a strong signal. Obviously the AGC has a problem, perhaps the decoupling capacitor and/or resistor needs replacing.

The crackles from the tuning spindle seem to be due to the coil and tuning subassembly to which it is attached being mounted on rubber insulators with one earthing wire to the main chassis rather than being mounted onto the main chassis.
I can't at present see a solution, I can't fit a spring grounding blade as that will ground the subchassis as well. It is obviously not meant to be solidly grounded otherwise the maker would not have gone to the trouble of building a separate panel.

[Mark Hennessy]

Not getting much feedback from others on the forum, but I carry on. Perhaps all are bored with my restorations?

I'm following. Just a bit jealous, as there's no chance of any work happening in my workshop at the moment - I can't see the bench beneath all the junk, and in fact I can't see any surface in there for the same reason. Every time I start trying to tidy up, I just get demoralised and give up. It got so bad that I did the software updates for this forum as a diversion from the state of the workshop.

This set is well outside my experience and knowledge, but I learn a lot from threads like this.

[Raditechman]

I assume it is a push pull output stage and with the fairly largish output transformer and speaker should sound good. Nice to read of your progress.
John

[boater sam]

Thanks for the interest guys.
Yes, push pull output.
In reality the output transformer is tiny, mounted on the 'speaker basket.  Because its got no DC current through it, the windings can be thinner and the core smaller without saturating. Its probably a trade off, one extra valve, cheaper transformer.
The mains transformer is a good size though.  Has plenty of oomph when you turn the wick up.  'Speaker is 8" but only cheapy.

You can see the economy of manufacture in the way its wired, components on long bare wires in mid air, there is precious little sleeving on any wires. There is one resistor connected one end to a valve holder tag, the other is in mid air with an insulated wire soldered on!
And yet there is a tuning eye, rather superfluous on an AM set.  Maybe just a sales gimmick?

[Murphyv310]

Nice set Sam.
Been following this thread with interest.
I've had a crackly spindle before but can't remember the set involved, it was a long time ago.