Pilot U650 connections

[Gabe001]

Dear forum members,

I'm after some help with a Pilot u650 radio I have just bought off auction. Eventually I would like to use the radio to play music from an mp3 player. I do have a fantastic GEC which works perfectly by plugging the output from the MP3 player into the 'pick up' and 'earth' sockets.

Unfortunately the Pilot is much more complicated and I need someone who can explain what the connections at the back are for. I cannot identify the earth or the aerial sockets on the Pilot radio. The 'gram' socket is the pu jack and presumably LS is a loudspeaker jack, but the rest are beyond me. See pics.

Many thanks. I'm a bit of an amateur as you may have realised.

[turretslug]

Hi Gabe and welcome- there'll be plenty of advice from the hive mind here on the forum.

First thing- did this radio come with any history? It's a rather nice set with potentially good performance and very much emblematic of its era, but it's now over 80 years old and, if it wasn't overhauled pretty thoroughly in the last couple of decades or so, it could be unreliable, a fire or shock hazard or all three of those! Whilst the overhaul components to ensure that it continues to be a good 'un for years are quite inexpensive and still commonplace, the time and skill to do so aren't necessarily so. Continuing to use an "unknown quantity" of a radio could mean that expensive and difficult to obtain internal parts may be permanently damaged otherwise. As I say, there is plenty of free and willing advice here and some will surely have knowledge of this model in particular.

I don't mean to put a downer on things, but using anything of this age that uses mains and other high voltages is a serious business. Sorry if I'm teaching you to suck eggs or misunderstanding anything but we all like folk to be safe here!,

Colin

[ms660]

If powered up.....

The connections/pins on the Dynamic Speaker plug/socket can present a significant high voltage shock if contact is made between them and the chassis.

The Ext L.S socket ….ditto as above if the internal isolating capacitors to those sockets are electrically leaking (which they probably are)

I might be wrong but I think the antenna and earth connections might have been via two fly leads that were connected to the antenna input circuit and the chassis respectively.

Lawrence.

[Gabe001]

Hi Colin thanks for the input. No history unfortunately. I have contacted someone local I found through this forum who is going to have a look at it for me shortly. There is a new power cable which suggests that the radio did receive some love recently, although the majestic g80 rectifier valve was broken (smashed glass). My involvement so far was limited to cosmetic repairs to the chassis and trying to source another type 80 full wave rectifier with the same base. I am not messing around with high tension circuits and the radio will remain off for now. I do want to try to learn a bit more about it though.

[Hartley118]

I have a slightly later but otherwise similar Pilot and hopefully that experience may be of help.

You’re right that the gram connection is via that quarter inch jack socket, which looks to be a replacement for the original. If it’s connected the same as the original, inserting the jack plug will disconnect the radio signal, leaving the pickup signal to feed the audio amplifier stages. That would be the best connection for the headphone jack of your MP3 player.

But first.......Does the set play? Does it smoke? The first task is to get it going- if it hasn’t had a recent service, it will probably need one or two internal components replacing. This forum can help you with that. Hopefully, replacements will be relatively inexpensive capacitors.

There are one or two eccentricities about that generation of rather imposing Pilot sets. Being of American origin, there are some cost-saving simplifications to the design, such as the aerial and earth connections usually being on ‘flying leads’ with clips to attach the external connections.

It looks as though the internal speaker is of the ‘energised’ electromagnetic type rather than permanent magnet. That’s why there are two extra wires going to its field magnet in addition to the two that connect the audio to the voice coil. They carry some 250volts so deserve respect.

Your set may also be unusual like mine in that the extension speaker (ex ls) sockets are not connected as is usual simply in parallel with the internal speaker, but connect instead to the primary of the output transformer. This makes them more exciting than usual, in that they both carry the 250 volt high tension supply and can give a nasty jolt if you touch one with the other hand on the chassis. This arrangement also means that any extension speaker must incorporate its own output transformer.

Having said that, the set incorporates a proper mains transformer so that the chassis is safely isolated from the mains supply.

Once any defective components have been replaced, you should find it a sensitive set capable of excellent performance on all wavebands. And that tuning dial with its back illumination is a magnificent sight!

Martin

[Gabe001]

Thanks Martin, Lawrence and Colin. Its due in for an assessment and electrical safety check in a couple of weeks. I'll report back when it's (hopefully) up and running and I'm sure the info you provided will help. Gabriel.

[turretslug]

Good luck with it- as you say, a relatively recent mains lead is a hopeful sign that the rest of the set has had recent TLC.

In the meantime, my OCD has prompted me into wondering how the loudspeaker and magic eye fit around each other....

[David G4EBT]

I thought when I saw the 'U' suffix that this would be a 'universal' set - that is AC/DC, which 'U' normally signifies, but it isn't - it's AC only, with a mains isolating transformer, so is safer than it might otherwise have been, had it been a 'live chassis' set.

Many sets have a twin socket for 'Gram' and a 'Gram' position on the wave-change switch which mutes the RF/IF stages, leaving just the AF stage in use. However, in this set, the jack socket is an original feature - not a modification, and mutes the RF/IF stages when a jack plug is inserted. An MP3 player, I-phone or whatever inserted into the jack socket, may or may not need a pre-amp, but hopefully not.

Looking at Trader Sheet 582, given that the set dates from 1936, I'd certainly want to be sure that any paper tubular caps (especially C19 & C24) and electrolytics have been replaced, and that any perished rubber insulated wiring has also been replaced. It would be interesting to know if it has its original mains energised speaker, with its field coil (which doubles as a smoothing choke) still intact and situ. As often as not, due to failure of the field coil, some 'restorers' take the easy route and rather than re-wind the field coil, fit a permanent magnet speaker, replacing the field coil with either an LF choke or a resistor for smoothing, which in this case would need to be 1,400 Ohms (or most likely the nearest preferred value, 1.5k).

Pre-war sets do have a certain charm about them, but tend to be geriatric and needy 'money pits', with replacement valves often hard to come by and expensive.

Hope that's of interest.

[Gabe001]

Thanks David. The broken majestic type 80 full wave rectifier costs about £80 to replace with a like for like valve. I sourced a different brand full wave rectifier at a more affordable price which has the same base and I'll soon find out if it is electrically compatible.

Am I correct in assuming that the correct plug for the pu jack is a 6.5mm single pole banana type connector?

[David G4EBT]

Originally Posted by Gabe001

Thanks David. The broken majestic type 80 full wave rectifier costs about £80 to replace with a like for like valve. I sourced a different brand full wave rectifier at a more affordable price which has the same base and I'll soon find out if it is electrically compatible.

Am I correct in assuming that the correct plug for the pu jack is a 6.5mm single pole banana type connector?

No - not a banana plug - it looks like you need a mono 6.3mm old style jack plug, which acts as a switch to open the circuit from the RF/IF stage, while at the same time, giving you the two contacts for the audio input. The jack plug you needs looks rather like the plugs used on electric guitars. You can also get an adaptor plug with a 'phono' socket on the other end, which saves having to wire the jack plug up. You can then use a phono leads with say a 3.25mm pug or whatever at the other end for an MP3 player or whatever. Like this:

https://www.ebay.co.uk/p/RCA-Phono-t...61911043&rt=nc

Hope that helps.

[Gabe001]

Thanks, just ordered this from AliExpress, as I already have a male to male 3.5 mm stereo jack cable.
Jack 6.35 mono 6 corners AUDIO CONNECTOR&ADAPTER 6.35MM MONO PLUG TO 3.5 STEREO/MONO JACK 3PCS/LOT
https://s.click.aliexpress.com/e/lhmY9Jzq

[Gabe001]

Hi, just an update on this radio. I've taken it for a check up to a person I found via this forum. It had a shorted capacitor which was replaced. The replacement type 80 rectifier valve from langrex was a good and inexpensive replacement for the majestic type 80 which was smashed. I'm posting some more pics. The sound is great and the way the dial lights up in segments and the green magic eye look quite impressive.

Just waiting for the 6.3mm jack plug to arrive (from China) now.