Evaluation of my Ekco PB189 before restoration starts.

[vintage_8bit]

So I used metal polish as suggested by Stephen. I only had Brasso, so used this and a cotton rag. The more stubborn bits I used a fiberglass pencil dipped in the brasso, but used only light pressure as these can be harsh. I cleaned the finger contacts with very fine emery paper. All contact surfaces were then cleaned with Isopropanol.

The result was a lovely shiny selector disc. This gave a much smoother feel when manually tuning, it also squeaked before. The automatic tuning now works a treat. Just a small spark when it stops.

I found it interesting that when the station finger stops are not quite in the right place how good the discriminator tunes the station in. You can here this when the white button is pressed in for manual tuning and the station goes off tune as the discriminator is switched out.

[cathoderay57]

Nice work, well done

[vintage_8bit]

This might be a silly question and show my lack of experience but....

Just started allignment. Once the I.F. and discriminator have been set, you move on to S.W. The trader sheet askes you to adjust at 16.6 and 17.6 meters and check tracking at 50 meters. Im ok with that, but where are those points on the dial. The last marked is 18 meters. See attached. The medium and longwave adjustment points are easily identfied. You can see my guess marked on the attached. Due to the square dial the scale markings are of course non linier.

[vintage_8bit]

Moving on to the allignment now.
I.F. set up ok. Discriminator ok. Short wave ok. When I move on to M.W. I can set it up but C50 is right on the end of its travel. The screw is quite loose. C41 and C44 are also screwed right out? I had a look at the L.O. frequancy compared to the incoming r.f. On shortwave the L.O. is lower by 126k on medium and long wave its higher. Is this normal. I just assumed it would be one or the other not a mix of the 2.

I have changed C6, C10 & C11 for other reasons, as stated previously.

Colin.

P.S. Circuit ref to trader sheet 765

[vintage_8bit]

Just to add, I just looked at my Ekco A28 and the local oscillator is tuned high on M.W. and S.W., which I think is more conventional? So do I have a problem with the local oscillator on S.W. As C49 is adjusted first on S.W. this would offset M.W. and give me the problem with the M.W. adjustment being on limit?. There doesn't appear to be enough adjustment on C49 to tune local oscillator high on S.W.

[cathoderay57]

Can you confirm that you are doing alignment per Trader Sheet instructions i.e. adjusting the oscillator coils cores on LW and MW at the LF end of the band and trimmers at the HF end? Otherwise, providing the scale alignment is reasonable and the signal strength acceptable I would not worry about the MW trimmer being at the end of its travel. I'm 99% sure that the oscillator should run higher on SW as well as the other 2 bands. There is no osc core on SW but it is easy to align the set to the image frequency by mistake, i.e. with a particular oscillator setting the set will respond to signals above and below the oscillator frequency (difference in frequency being the IF of 126.5kHz). Rule of thumb is that if the local oscillator frequency is higher than the received signal the lower frequency position on the sig gen dial or the higher frequency position on the receiver dial is the proper signal at which to align. If you are certain that you are using the right settings then the only other possible causes are that the dial pointer hasn't been set correctly and therefore you are in effect trying to align the set with a fixed frequency offset, or the SW coil former has suffered damp and/or shorted turns that has affected its inductance. If C49 is fully screwed in then you might be able to shift the frequency down by adding a small fixed value pF capacitor in parallel. If C49 is fully unscrewed I can't think of another fix. Cheers, Jerry

[vintage_8bit]

Thanks for the reply, its appreciated.

I can confirm I'm following in order, the procedure in the Trader service sheet.

With added confidence now, that the local oscillator should allways be high, I have had a look around the oscillator set to Short wave. Moving the chassis connection wire from the bottom end of L10, to different possitions I Can change the oscillator frequency by around 120kHz! Adding an extra parallel wire shifted oscillator further in the right direction. I was then able to align S.W. with oscillator set high. This also enabled C50 to be screwed in further when aligning M.W. The C10 earth wire measures just a few milliohm to chassis. Further investigations are needed but at least the local oscillator is now in the right area. I will report back on what I find.

Colin

[cathoderay57]

Nice work, well done

[vintage_8bit]

Just to finish off this thread.

I have now successfully aligned all three bands. The only other problem I had prior to success was with medium wave being increasingly deaf towards the high frequency end. This was because the tracking was out between the 2 front end stages, prior to V1.

The trader sheet askes you to adjust C43 during long wave alignment, this then affects the previous medium wave adjustment as well. I also noticed that C45 was not mentioned in the trader text. So after adjusting C43 during medium wave alignment, I then adjusted C51, C45 and L12 only for longwave.

The only other problem was the motor would some time "chatter" when moving as the dog clutch moved in and out of engagement. This was fixed by reducing the tension on the noise suppression switches operated by the end thrust of the motor shaft.

So another chassis restoration performed, just the case to do. I quite like the three Ekco sets I've now worked on, the previous being an A28 & U76.