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Old 27th Jul 2020, 4:19 pm   #1
vintage_8bit
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Default Evaluation of my Ekco PB189 before restoration starts.

Just been evaluating my PB189 before starting the restoration.
I have put in a request for a back card and speaker in the wanted section.

I have checked the transformers chokes and I.F.T'S all appears good. Powered up with no valves and checked the motor. So to me it looks like its worth starting. I have been looking forward to working on this one. I have allready tacked in a new decoupler, for a latter slow power up with some valves in.

Looking at the commutator there is a distinct ridge between 2 of the segments, see photo. The contacts catch on this. Has anyone else seen this. I would want to take the ridge flush but looks like its always been like this. From behind you can see the paxoline?, forming this ridge.
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Old 27th Jul 2020, 4:30 pm   #2
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Default Re: Evaluation of MYPB189 before restoration starts.

I look forward to your restoration, i have the PB199 waiting in the wings for its turn.
The ridge is normal and on all the ones i have seen.
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Old 27th Jul 2020, 5:16 pm   #3
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Default Re: Evaluation of my PB189 before restoration starts.

Thanks Stephen. I wonder if that's one reason why the contacts sometimes get damaged?
I intended starting this restoration after a Pye PE80, but thought I would just check first to see if the Ekco was worth restoring, and meanwhile it would then give me time to search out a back card and speaker. Trouble is I find it so interesting I can't put it down.
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Old 28th Jul 2020, 9:02 am   #4
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Default Re: Evaluation of my PB189 before restoration starts.

Hi I have repaired several of these ,and I have in my collection a Mc Michael motor tuned which has the same mech , first make sure the fibre gears are in good order ie no teeth missing ,if all ok and the mech seems free to run , switch on and press a button ,this will tell you if the motor is ok , it is an ac motor no brushes , Oh I would remove the rectifier to be safe, It looks like you will need to make some contacts, this is normal for these . If you search on the forum there are one or two posts regarding the radio, Mick.
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Old 28th Jul 2020, 10:25 am   #5
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Default Re: Evaluation of my PB189 before restoration starts.

Thanks for the advice Mick. I have removed all valves and disengaged the motor from the commutator. I removed the rear plate to inspect the gears. All seems well here. I can see some wear on the fibre gear but not enough to cause trouble. I then powered and was able to see the motor turning freely. Did you lubricate your gears?

I have since replaced, just the rectifier valve and output, slowly powered and I have a healthy sounding buzz when the grid is touched.

Now I know where I am with this set, I am now going to carry on with my Pye PE80. Hoping to return to the Ekco shortly. Meanwhile looking for a back and speaker for it.
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Old 28th Jul 2020, 9:49 pm   #6
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Default Re: Evaluation of my PB189 before restoration starts.

The last one of these I restored, I couldn't peak the automatic frequency corrector circuit in accordance with the instructions in Trader Sheet #765. This involves adjusting the discriminator cores of L18 and L19. It turned out that the capacitors C17 and C18 had drifted way off 140pF. They were the infamous white porcelain "pyjama button" types that often fail. If you have trouble peaking the discriminator and/or the alignment then also check C4 and C5 as they might be the same type. Cheers, Jerry
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Old 28th Jul 2020, 11:15 pm   #7
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Default Re: Evaluation of my PB189 before restoration starts.

Thanks Jerry. As there are a few of those and its a value I dont have I will have to stock up. Seems you can buy quantities of these for just a few pounds.
Apart from a couple of places the component layout all seens reasonably accessible, now the dust is blown out. Not sure about inside the cans yet.

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Old 1st Aug 2020, 1:46 pm   #8
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Default Re: Evaluation of my PB189 before restoration starts.

I now have a back board and speaker as well, so thanks to Mark for that.
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Old 8th Aug 2020, 12:32 pm   #9
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Default Re: Evaluation of my PB189 before restoration starts.

I just started to re-cap. Ive noticed a discrepancy between my radio and the circuit diagram (Trader 765). R36 on the feedback from T1 is missing?. Also C35 should be a .2uF but a .1uF is fitted?. Fortunately I have an identical set. This appears to be wired the same.

R36 on layout is shown on the tagboard next to T1. 1 of 5 resistors, R30, R29, R1, R17, and R36. I only have four resistors here. Same as the 2nd chassis. R35 sits the other side of tag board.

I did try and find a manufacturer service sheet to compare but couldn't find one. Is this a mod perhaps?
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Old 8th Aug 2020, 4:56 pm   #10
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Default Re: Evaluation of my PB189 before restoration starts.

I have now removed C15 for re stuffing. Parts list calls up .1uF. Fitted is .2uF. So in wondering if just the values have been transposed on the parts list? The My other chassis is wired the same. Still have a missing R36? On both chassis.
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Old 8th Aug 2020, 10:25 pm   #11
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Default Re: Evaluation of my Ekco PB189 before restoration starts.

I wouldn't worry too much about the discrepancies. Certainly the use of 0.2uF in lieu of 0.1uF is not going to make any difference. The presence, absence, or discrepancy in values of C35 and R36 in the negative feedback loop are unlikely to make any significant audible difference - we're not talking hi-fi here! If it were me I would revert to the Trader Sheet wiring and component values, and see what happens. If the set performs adequately then job done. Occasionally there are errors in Trader Sheets, but few and far between. Sometimes capacitor and resistor values are changed by fixers over the years that can be masking other problems i.e the symptom is fixed but the fault isn't. In this case, that is extremely unlikely. Cheers, Jerry
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Old 8th Aug 2020, 10:56 pm   #12
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Default Re: Evaluation of my Ekco PB189 before restoration starts.

Thanks for your reply Jerry. Yes, I would of gone with the trader sheet, but when I realised my second chassis was exactly the same, regarding values of C15 & C35 and there are no signs of R36 ever being fitted I wondered if anyone else had seen this before. 1st chassis serial No J24631, 2nd chassis J25227. The sets came from different places, they only just met on my bench. I have lots more waxes to change before the big power up....
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Old 16th Aug 2020, 4:12 pm   #13
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Default Re: Evaluation of my Ekco PB189 before restoration starts.

Almost changed all the caps.
The tone control and on/off switch (R33) had an open circuit one end of track. Also mains switch was o/c. I've striped it down to clean, I can see a track cut near the end, see photo. It looks deliberate at manufacture. I have not seen this before. Is this normal? The only reason I can see is to completely remove the tone correction when control fully clockwise, for some reason.
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Old 16th Aug 2020, 4:26 pm   #14
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Default Re: Evaluation of my Ekco PB189 before restoration starts.

Can't imagine why the manufactures would do it, looks like it's about 5k from the 60k
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Old 16th Aug 2020, 5:14 pm   #15
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Default Re: Evaluation of my Ekco PB189 before restoration starts.

May be its had some current flowing through it and it just looked to me like a cut? It didnt look like the pot had been apart before.

This set looks like its been powered along time ago with leaky caps as there were a few waxes with bulging ends.

Someone in the past had wedged in an oversised cap somehow in to one area. It was an oil filled paper? of the correct value, in place of an electrolytic. I think the main twin smoothing cap is not original.

The radio was a loft find. The current relatives had no recollection of it.
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Old 16th Aug 2020, 5:21 pm   #16
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Default Re: Evaluation of my Ekco PB189 before restoration starts.

It was so often the way that when an expensive purchased TV or Radio was eventually updated, the owners couldn't bear to part with them, so if it fitted through the loft hatch that's where they stayed.
By the time they moved out it was so outdated they often couldn't be bothered or forgotten entirely.
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Old 16th Aug 2020, 6:47 pm   #17
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Default Re: Evaluation of my Ekco PB189 before restoration starts.

The tag to the broken end looks like it's never been soldered to anything. If this is the case then the cut in the track is unimportant.


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Old 16th Aug 2020, 7:00 pm   #18
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Default Re: Evaluation of my Ekco PB189 before restoration starts.

As it only goes o/c near the end of travel I can live with that. I just wonder how a cut / break like that was formed so neatly. Just cleaning the on / off contact now.
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Old 26th Aug 2020, 9:40 pm   #19
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Default Re: Evaluation of my Ekco PB189 before restoration starts.

We haved moved on.
All waxes and electrolytics changed.

Powered up ok. But I.F. way out. 1st I.F. without touching adjustment peaked at 127kHz, but second I.F. at 175kHz. Changed all the 140pF button ceramics (Thanks for the advice Jerry) and freed off the slugs while I was in the cans. Without any adjustment the I.F.'s are now very close to nominal of 126.5kHz. All the 5 x 140pF were as good as O/C and cracked.

2nd problem, intermittent crackling on medium wave. This was traced to C6 (Trader)

3rd problem, no longwave, this was due to C11. I also changed C10 which didnt seem to be causing a problem on medium wave but had drifted way out of tolerance. C6, C10, & C11 were all marked with Sator, made in Austria.

Bit of a challenge to undo, and do up one of the retaining nuts on the local oscillator can. This was due to accessibility!

I found heating the can retaining nuts freed them nicely from the locking paint, providing they are moved whilst still hot.

Its now ready for allignment.

One question. The selector disc needs cleaning. It has a fair bit of suface corrosion. I was thinking of a gentley using fine 0000 grade wire wool and oil. Then a clean with isopropanol. Any ideas welcome.
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Old 26th Aug 2020, 10:02 pm   #20
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Default Re: Evaluation of my Ekco PB189 before restoration starts.

I used Peek metal polish and a green scouring pad, results were very good.
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