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Old 22nd Feb 2018, 4:25 pm   #261
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Default Re: Bush A.C.91

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Originally Posted by DonaldStott View Post
Lastly, for now, I'm still intrigued (perplexed?) by some undocumented wires and connections in and around V5 - the common chassis tag for C27 and C29 has a wire running to Pin 3 on V5 and from there another short wire leads to another chassis tag. I've no idea what these are for or what they are doing as Pin 3 in unused in V5??
Manufacturers often used unused valveholder pins as 'anchor tags'. Quite simply if there was a spare, unused pin on a valveholder it could be used as a convenient solder tag for other wires connecting to other parts of the circuit.
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Old 22nd Feb 2018, 4:29 pm   #262
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Default Re: Bush A.C.91

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Manufacturers often used unused valveholder pins as 'anchor tags'. Quite simply if there was a spare, unused pin on a valveholder it could be used as a convenient solder tag for other wires connecting to other parts of the circuit.
Acknowledged - but these are connections from chassis tags to the unused valveholder tag for Pin 3 in V5 - they seem to serve no purpose??
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Old 24th Feb 2018, 12:54 pm   #263
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Default Re: Bush A.C.91

Earlier this week tim.norris mentioned " ...have not had problems with hum from heater wiring . is the screened wire to the cap of v3 the ebc 33 in good condition ,have you metred both the outer and inner wires through ? " I was so wrapped in possible issues with V4 that I forget I hadn't checked continuity through the co-axial cable running to the V3 top cap.

Guess what - I checked continuity and got the usual beep from the screen and then nothing from the inner conductor! Looking inside the V3 cap it was immediately clear that the inner conductor had snapped and was touching the middle of the valve cap - see attached picture! Thanks Tim! So looked out a new length of co-axial cable and replaced the existing - my goodness it's a tight fit.

Switched on the set, waited for the valves to heat up - no real hum and the radio literally blasted into life !!!


Can't believe that I now have stations on Short Wave, Long Wave and countless stations of Medium Wave - all at a very good volume but with lots of background noise. Really can't complain as the set is seriously alive for the very first time!

Thanks to everyone for their for their patience, help and support - don't know if I need to replace CL33 now?? I had to pluck up the courage to Post this update on the Forum as its a bit embarrassing but hopefully this may be of some help to others?

As David G4EBT reminded me "Just goes to show - it can often be the simplest of things that can lead you a merry dance."

Final tasks are related to what can be done with that residual background noise - am I expecting too much? I've removed all possible causes of interference from other sources?

Meantime I remembered that some "idiot" had inscribed deep scratches on the front and side (see attached picture) - I've tried various things to fill these in and have had some limited success with Dark Wood Scratch Cover - as it's a blend of waxes and colouring agents it flows into the scratches leaving some dark wax behind when polished. I did this about half a dozen times and its looking a lot better already.

I'm looking to build up the scratches rather than sand the Bakelite down as they are too deep. I tried running molten dark wax into the scratches but it simply wont stick and lifts off when using a razor blade. I know that on the Forum many suggest Super Glue and then sanding that down but I'd be concerned about taking the face off what is otherwise a very good Bakelite case.

Nearing the end now (collective sigh of relief !!!) having finally laid low the ghost of "The Phantom" - its been a roller coaster ride and I almost through in the towel several times! But what an education it has been and I don't think there is a single area of this set that has not been restored in some way!
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Old 25th Feb 2018, 3:01 pm   #264
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Default Re: Bush A.C.91

I think it should 'high fives' all round that you've stuck at it and seen the job through to a successful conclusion!

It's quite a challenging set anyway for a newcomer and it had been seriously got at by a previous owner, which meant that before you could begin to restore it, you had to put the set back to how it should have been before the 'phantom' messed with it. You had the added complication of the fractured cores in the IFTs, which might well have been why the 'phantom' threw in the towel (or was he the culprit who caused the damage to the cores?). Nevertheless, with the help of '60 old john' you managed to source a pair of IFTs and fit them, then discovered the elusive open circuit in the top cap.

Although you've had a roller coaster ride and have incurred considerable expense beyond what you might have expected, it's been time and money well spent and you've learned more from this one restoration that some people learn from a dozen straightforward sets which are working when they get them, and they just routinely replace the waxy caps. You've ended up with a 50s classic set, fully restored, fully working and safe, and not as commonplace as the DAC90A.

The experience, self-esteem and confidence that you've gained will stand you in good stead for future restorations, and you can justifiably claim that you don't just 'do up' or 'mend' radios, or 'get them working' but restore them, diagnosing and rectifying faults step by step as you embark on a 'journey of discovery' from a dud to a working set, which is quite another thing!

A lengthy thread with lots of input from forum members, (more than 260 posts and 13,800 views!), which should encourage and inspire others.

The only question now is: 'What are you going to do for an encore?'
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Old 25th Feb 2018, 5:24 pm   #265
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Default Re: Bush A.C.91

Pleased you have managed to get the set working. You mention a lot of noise, what is the situation with C30 Mains RF bypass capacitor ? Unfortunately there are many items in use today throwing out hash. I think I said about the FM to AM sender unit, make one, find the quietest part of the band and tune it in there.


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Old 26th Feb 2018, 11:19 am   #266
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Default Re: Bush A.C.91

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I think it should 'high fives' all round that you've stuck at it and seen the job through to a successful conclusion!
As you know David G4EBT without your encouragement, enthusiasm and seemingly boundless expertise I would never have seen this project through to conclusion!

At times it was like having my very own Tutor as I was mentored through many areas of vintage radio theory along with detailed instructions on many practical aspects - hopefully some of this knowledge will have been retained by me!

Many others also contributed to this successful outcome and I would single out tim.norris in particular for the supply of replacement components and additional support/know-how. The replacement IFT coils from 60 oldjohn were really the icing on the cake as it was surmised quite early on that this was a showstopper - I still haven't opened up the faulty IFT coils to investigate the ferrite slugs - maybe one day?

Expert knowledge, patience and perseverance were also supplied in abundance from the following Forum Members/Moderators along with other components which were kindly supplied/donated - ms660 (Lawrence), AC/HL, Station X (Graham), Voxophone (Liam), Phil G4SPZ, Boater Sam, Herald1360, 'LIVEWIRE?', Cobaltblue (Mike T), Nuvistor, Radio Tech (Ken), PJL, Ed_Dinning (Ed), SWB 18 (Phil) – if I’ve missed anyone then sincere apologies. This really has been a collective Forum effort!

Still got that bit of residual background noise but perhaps, as I said, I am expecting too much. Searching through the Forum and other online sources there are references to “noisy resistors” – what do you guys think?
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Old 26th Feb 2018, 11:34 am   #267
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Default Re: Bush A.C.91

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Pleased you have managed to get the set working. You mention a lot of noise, what is the situation with C30 Mains RF bypass capacitor ? Unfortunately there are many items in use today throwing out hash. I think I said about the FM to AM sender unit, make one, find the quietest part of the band and tune it in there.
Thanks again John for the replacement IFT colis!

I've already replaced C30 with a modern X2 type capacitor across the mains.

I've tried isolating the set from external sources of hash - LEDs, phones, power supplies etc.
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