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Old 30th Mar 2020, 5:20 pm   #1
Devon60Ben
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Default Pilot U650

Good Evening all,
My first ever radio project is now on the bench having bought it last Easter but now being isolated at home for 2 weeks at last I have the opportunity to look at it. (sorry if waffling too much)
Anyway although the wooden housing looks to be in very good shape the chassis has plenty of dirt and rust and a cut off power cord (no fuse holder present) and a seized chassis screw.
The tuning mechanism was very notchy and semi stuck so I started there and cleaned out the old grease and, freshly lubed, it now works well.
The dial lamps have also been replaced and set aside as only 1 was working.
Don't know much of the history of the radio but the previous owner has attempted to get it running in the past and there are two massive LCR brand motor run type filter caps installed under the chassis (wedged and taped) replacing the 2 can caps which have been bypassed but left in situ. I will remove these and see if I can re-stuff the original cans for cosmetic reasons and to remove these aweful looking filter caps!
In fact, all the caps and resistors look like a dogs dinner and replacement resistors made up of 2 or 3 in one case have been joined in series or parallel to make up the values. These will all be removed and replaced back to the original specs in my 1936 schematic which was downloaded from a museum site.
Checked the power transformer and getting positive vibes which is promising - an isolated chassis is also nice rather than live. Will await the rebuild before energizing on the variac / dim bulb / isolation transformer unit.
All the valves appear to be correct and unbroken but I cant test them yet as my valve tester doesn't have the right sockets for 4 and 6 pin valves. The speaker is a Magnavox replacement of similar design to original but has had a cone repair - not sure about this yet - will leave this until later.
Will recap & re-resistor first then check all wiring ok or replace any that needs it.
Have the tone control and volume pots in bits at the moment for a clean and lube - the on off switch on the back of the tone control is working again after initially being sticky - good old Servisol!
Have ordered a couple of new knobs as these were broken so as parts come in will progress as planned.
Thanks in anticipation for any guidance / help when needed which I'm sure it will be.
Cheers, Ben
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Old 31st Mar 2020, 6:17 am   #2
Devon60Ben
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Default Re: Pilot U650

I have taken a few pictures to document the project before I start to replace anything.
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Old 31st Mar 2020, 9:08 am   #3
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Default Re: Pilot U650

There is a revised Trader sheet 582 in the service data link at the top of the page, may be worth the 1.99 In case it is more of a match for your radio.
I will enjoy watching the restoration.
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Old 31st Mar 2020, 9:59 am   #4
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Default Re: Pilot U650

Very challenging for a first restoration! I also recommend you get the later trader sheet (582) as this can be used for the component layout. It looks like every component has been replaced with whatever was at hand from a rather limited selection.

Before you start you should check the continuity of the mains transformer, output transformer and speaker field coil.

As you can't trust that any of the wiring is correct due to the vast number of component changes, I would strip all the new parts out, check the remaining wiring is correct whilst the chassis is empty, and only then fit a completely new set of components double checking as you go by marking up on a copy of the trader layout.

Last edited by PJL; 31st Mar 2020 at 10:07 am.
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Old 31st Mar 2020, 10:09 am   #5
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Default Re: Pilot U650

Hi Ben,
I have to agree with you that all the components are a 'dog's dinner'! It looks like almost everything has been replaced with whatever came to hand. The two motor caps are especially fine!!

There is a good selection of fabric covered mains leads available on Ebay. I've found some almost exact matches for '30's sizes & colours. They are modern 2 or 3 core pvc flex with a woven fabric outer in various colours. They look very good.

Good luck with what will turn out to be an interesting restoration!

Cheers
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Old 31st Mar 2020, 10:27 am   #6
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Default Re: Pilot U650

Looks like the circuit is a must for this one Ben ,I would rip out all the previous repair and start again all the help you will need is on here,good luck with it , Mick.
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Old 31st Mar 2020, 11:49 am   #7
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Default Re: Pilot U650

Goodness me! You do wonder what was going on in some folks' minds when they were doing things. Perhaps the thinking went along the lines, "capacitors are used to reduce interference, so the higher the value the better". Who knows. They may at least be useful in another project as wattless droppers, or high-voltage reservoirs. I suspect that a set like this would have used pre-preferred value type resistors, so maybe they thought that they'd better make them up precisely with modern types to the original values. Someone with more experience under their belt would have known that many valve circuits (particularly domestic radio) are very good-natured as regards this sort of thing and are just fine with "nominal" values. I do worry that when those with clout come across kludges like this that it only increases the pressure for access and repair generally by consumers to be increasingly verboten- not good for the sustainability movement.

That said, I hope that the overhaul goes well, I think that pre-war sets like this are something of a technology emblem of the era, and some can be appealing pieces of furniture to boot. Cleaning up a fouled tuning arrangement and finding a vast improvement in action must be one of the most satisfying aspects of an overhaul. Not to mention that at times like this having something absorbing to get stuck into can be therapeutic! I agree that a continuity check on the components mentioned by PJL is important as a first move before investing further time, money and effort though, also powering up the mains transformer via lamp limiter to check for shorted turns. Good luck with it, Colin
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Old 31st Mar 2020, 11:50 am   #8
Devon60Ben
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Default Re: Pilot U650

Thanks to Mick, Nick, Frank and PJL.
I now have the 582 trader sheet and the schematic plus various other things like the valve voltages and band frequencies plus alignment procedure.
I like a challenge and while I expect that my skills are a bit scruffy - have plenty of determination - and not much else to do at the moment.
Mains transformer continuity checked out ok and output transformer too.
The lamps have arrived so will replace those - only one of 6 work at the moment.
Considering the above advice and potential help on here have decided to remove everything from the circuit and start again.
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Old 31st Mar 2020, 12:29 pm   #9
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Default Re: Pilot U650

Sorry Ben, I've just re-read your first post and I now realise that the two big blue LCR capacitors were being used as HT filter caps, rather than mains bypass- I was misled by the blue and brown wires. That's not so mad after all- one thing to beware of is that the off-load/initial switch-on HT can be far higher than the running HT. In particular, pre-war sets very often had a fast-heating directly-heated rectifier with a high forward voltage drop and a high-resistance smoothing network- this can result in an HT supply of a typical 250V or so being double that for 20 seconds or so until the other valves have warmed up. 500V is right on the limit of mainstream electrolytic capacitor voltage availability, so the previous repairer may have chosen the big LCR motor run types with good reason, these types usually have their AC voltage rating printed on them, but a DC voltage rating of typically around 630V somewhere in the spec. sheet.
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Old 31st Mar 2020, 12:59 pm   #10
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Default Re: Pilot U650

This is the only underside view I can find of a U650 although it is in fact the almost identical X65B. https://www.vintage-radio.net/forum/...d.php?t=163302

This one already has some parts replaced but it will help you identify any remaining original parts. You will notice that the set used 'dog bone' resistors and I can only see one in your picture (100K with yellow dot).
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Old 31st Mar 2020, 2:52 pm   #11
Devon60Ben
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Default Re: Pilot U650

Quote:
Originally Posted by turretslug View Post
Sorry Ben, I've just re-read your first post and I now realise that the two big blue LCR capacitors were being used as HT filter caps, rather than mains bypass- I was misled by the blue and brown wires. That's not so mad after all- one thing to beware of is that the off-load/initial switch-on HT can be far higher than the running HT. In particular, pre-war sets very often had a fast-heating directly-heated rectifier with a high forward voltage drop and a high-resistance smoothing network- this can result in an HT supply of a typical 250V or so being double that for 20 seconds or so until the other valves have warmed up. 500V is right on the limit of mainstream electrolytic capacitor voltage availability, so the previous repairer may have chosen the big LCR motor run types with good reason, these types usually have their AC voltage rating printed on them, but a DC voltage rating of typically around 630V somewhere in the spec. sheet.
The motor run caps were 440V so I have ordered some 500V electrolytics to replace them which look to be about half the size too.
These were indeed not easy to find but are now in transit
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Old 31st Mar 2020, 3:02 pm   #12
Devon60Ben
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Default Re: Pilot U650

Quote:
Originally Posted by PJL View Post
This is the only underside view I can find of a U650 although it is in fact the almost identical X65B. https://www.vintage-radio.net/forum/...d.php?t=163302

This one already has some parts replaced but it will help you identify any remaining original parts. You will notice that the set used 'dog bone' resistors and I can only see one in your picture (100K with yellow dot).
Thanks PJL, thats a helpful picture as the layout drawing on the 582 sheet is very dark and hard to see clearly. There are 2 more dog bones in my radio, a 400 ohm on V1 and a big 410 ohm (5W possibly) on V5 which is also there on the photo you found - I like the look of these - will test them and see how they measure. is there a way to determine the wattages of the dog bone resistors and therefore the replacements required if not on the schematic / circuit diagram other than finding a similar size?

Small dog bone on v1 pic attached
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Old 31st Mar 2020, 3:54 pm   #13
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Default Re: Pilot U650

Hi, I have exactly the same model and I attach an underside picture of mine, if this helps. I do have a higher resolution picture but I'm unable to upload it.
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Old 31st Mar 2020, 4:10 pm   #14
Devon60Ben
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Default Re: Pilot U650

That looks great Gabe, so much cleaner than mine.
While I have been waiting for parts I have cut out the components and de-soldered loads of stuff - some connections had several clipped off legs attached from multiple replacements.
One thing I have no idea about is what type of antenna to attach to the flying leads?
And did the radio have a back cover? Mine just has the chassis open to the world?
Many Thanks
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Old 31st Mar 2020, 10:59 pm   #15
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Default Re: Pilot U650

Mine has a back cover. I dont think the cover is original (as it is branded a PYE) but the markings seem to match the sockets at least. I'm attaching a picture. Re the aerial I don't really listen to any AM radio stations, and the puppy will make mincemeat of any loose wires on the floor, so mine isn't connected; it's in use daily via the PU socket. The 3mm wander plugs I use in the other radio set are too small for the aerial socket on this set, so you probably need 4mm banana plugs, and a long piece of wire of course
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Old 1st Apr 2020, 6:34 am   #16
Devon60Ben
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Default Re: Pilot U650

So I have an antenna wire connected to chassis ground and another feeding into the switch unit - both have no plugs on the ends and there are no places to create sockets on the chassis unless I create some.
So I was considering attaching banana plugs and then making a small bracket to mount onto the inside of the wooden cabinet that holds sockets for these banana plugs to plug into with provision for external antenna wires to also plug in at the same point.

The pic shows the chassis ground between the bases of V1 & V2 and the other wire above it - both are hanging out to the right of the picture.

It looks like I will be able to make something similar to your back panel Gabe, thanks for adding your picture. Not sure about the intricate arrangement of slot holes though that looks tricky.
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Old 1st Apr 2020, 7:27 am   #17
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Default Re: Pilot U650

The circuit diagram on Trader 582 seems to show antenna and earth sockets, are you sure there are none on your set.
I have never known a set where the antenna and earth is hard wired into the radio.
Just thought, maybe the sockets were originally mounted on the card back and what you have there now are the 2 short wires which went to the sockets.
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Old 1st Apr 2020, 8:12 am   #18
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Default Re: Pilot U650

It was quite common on American sets (and late 30's Cossor sets ) to connect Aerial and Earth via a flying lead with a Fahnestock connector

https://reverb.com/item/2996870-fahn...age-of-6?pla=1

No idea why as its annoying!

Cheers

Mike T
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Old 1st Apr 2020, 8:12 am   #19
Devon60Ben
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Default Re: Pilot U650

I thought it was a bit odd Mike but assumed something had happened along the way.
Attaching to the wood seems more secure than the hardboard back unless I use thin ply for the back. There is no sign of anything having been attached to the internal sides of the cabinet before though.
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Old 1st Apr 2020, 8:28 am   #20
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Default Re: Pilot U650

It was common to see American sets without backs they were not fitted by the manufacturer.

They seem to have arranged things so there were no live connections to touch on top of the chassis.

Not the case with AC/DC sets though.

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