Fidelity portable valve record player power supply

[Bornatotter]

Picked up a cute fidelity portable for a fiver. The plugs been cut off. I’ve had the same issue on a Dansette Junior which has a very similar set up but they at least give you a clue with the core colour coded bronze and silver for live and neutral. Sadly not on the fideilty. I will swap out the old bell wire for some modern flex but was just after some confirmation on the connections to the volume on/off pot. I’ve attached some pics and I’m fairly certain that live solders onto the tag adjacent to the brown wire and the neutral to the tag next to the black wire. Just want to be sure before I hook it up. Any help appreciated. Totts

[Station X]

I'm assuming this is a live chassis player with U series valves?

Generic answer.

Turn the player on and measure the resistance from each white wire to the chassis. Connect the NEUTRAL BLUE wire to the tag whose white wire shows the lowest resistance.

It'll most likely be the tag adjacent to the black wire, but best be sure.

[Bornatotter]

Cheers Graham

[Bornatotter]

Been a while since I pulled this one off the shelf. Powers all good and motor running but there’s now a loud hum and some smoke coming from the green component (capacitor?) feeding into the UY85 valve at the first stage of the amplifier - the green component appears to be marked 150 ohm. Seems like it’s burnt out? Any advice on replacing that part appreciated. Just looking to make sure I’m using the correct part. Totts.

[Edward Huggins]

The green component is the surge resistor and these do run very hot. If this is smoking, it's liable that the main reserviour and/or smoothing capacitors may have failed and will need changing oot. If not that, then check the UY85 rectifier valve. If, as well as other components you do replace the 150 ohm surge resistor, do make sure it is rated a 5 watts or more.

[ekjdm14]

The green component is a 150R resistor, probably 2 or 3 watts rated i think and the UY85 isn't a "stage" as such, it's the rectifier valve.

It could be (likely IMO) that the electrolytic capacitors in the can have failed causing the hum and it's also probable that the wax coupling capacitor to the UL84 will have been leaky and this could destroy the valve and output transformer in short order. This could also account for the smoking resistor with excess current draw.

I'd start by checking the coupling cap for leakage/just replace anyway if it's a wax cap. Then check the electrolytics and replace if they're open & only then check the resistor to see if it's cooking has made it change value and replace if needed.

When the caps and resistor are in order, you could power up again and hope the valves/OPT survived. Be aware when testing that there is potentially high voltage present even when switched off if the electrolytics are OK, check for DC voltage between the section's tags & the chassis and allow to discharge before getting fingers near anything.

(This is not a full run-down and I am by no means an expert, but I do have a Fidelity player with this chassis (and that had a dead output transformer when I got it!)

[Bornatotter]

Cheers Dan. Appreciated.

[ms660]

The 150 ohm resistor looks ok at first sight, measure its resistance with the record player unplugged from the mains supply.

So far as I can make out looking at the connections to the valve sockets in the photo's it's a UY85 & UL84 job.

Lawrence.

[Bornatotter]

Dan. Does look like the wax coupling cap to the UL84 is leaking and shot. Just wanted to check if you know what an appropriate replacement component for that would be? Can post a better pic if need be. Totts

[ekjdm14]

It should have it's rating on the side under the dirt/waxy gunk (be careful not to wipe the numbers off if you have to clean it to read them!) I fear I mis-spoke before and it's not as much a grid coupling cap but in the tone circuit, either way though it's a "waxie" and worth replacing. From memory mine was 0.04uF/400v but I could be way off.

[ekjdm14]

I've just pulled up a schematic of a similar player and from looking, the waxie could put undue stress on components if very leaky, seems to have around 250v across it & the tone pot so leakage would draw current through the OPT and tone pot.

[ms660]

In the photo's so far, I can only see a resistor with some wax on it (680 ohms cathode bias resistor) no wax coupling capacitor, g1 appears to be directly connected to the wiper of the volume control.

Lawrence.

[Bornatotter]

Thanks Lawrence. Will send post some better pics. Totts

[Techman]

It sounds like you've been unlucky and the smoothing capacitor has gone very leaky internally - it's the one in that round silver can mounted on the chassis. It may possibly recover if you switch it on for a moment until you hear the hum in the speaker, then quickly switch it off and leave it for a few minutes before switching it back on again, repeating this a number of times to see if the hum level gradually decreases and that poor resistor stops smoking.

I have to point out some possible dangers with this record player. You no doubt realise that it has a live chassis, in that the metalwork of the amplifier is connected to one side of the mains, so make sure the mains lead is connected appropriately in the plug. You've already been told about this in an earlier post, but unfortunately there's no colour coding on the mains lead on these, so you'll have to check it with a meter to confirm connection, then mark it with a felt tip pen on the all white insulation before fitting a plug.

There's absolutely no isolation on these, in that there's a direct connection from the cartridge connections under the pickup head (just where you put your fingers as you lift it onto a record) directly back to one of the pins on the mains plug, hence the need to make sure it's connected correctly as said previously. These players "are what they are" and would have just about conformed to the limited safety standard of the time when they were made. Don't try to modify it as you may run into trouble. There would have originally been insulation on the two cartridge connections in the pickup head, but this sometimes goes missing over time, so fit some small pieces of heatshrink if it's gone.

So to sum up, use the player carefully as it is, but don't allow it to be used by an unaccompanied child. Also, but only after unplugging it from the wall socket, check that the possibly faulty silver canned capacitor is not starting to become warm to the touch on its outer casing, as if it is and you were to leave the unit connected to the power, it can eventually go off with a bang and spatter its innards all over the place!

[ms660]

Another possibility is the output valve itself or the control grid return path via the volume control, if that goes open circuit for whatever reason the control grid will be floating meaning no grid bias and the valve will pass a lot more current than it's supposed to in that design which will increase the HT ripple voltage and possibly cause some of the components to overheat.

Lawrence.

[Techman]

I've just remembered a couple of other important points regarding this player. There's no cord grip on the mains lead on these, so if the cable were to be pulled or tripped over a few times, it could be possible for it to be pulled off its connections on the switch. If this were to happen, there's a very small, but possible chance that the live end of the cable could touch the deck metalwork or be pulled completely from the unit, in both cases causing possible electrocution to the user. The mains lead on these is basically twisted lamp flex, which is OK to use if it's in good condition, but not ideal and wouldn't be allowed under today's regulations. Some would recommend replacement, but this should only be done if you're competent enough to do the job properly, and it should only ever be of the two core type and a safety cord grip should be added within the unit - never attempt to fit an earth!

The other point is with regards to the cartridge. If you have to fit heatshrink to the cartridge connections, don't heat it while the connectors are fitted to the cartridge as any form of heat will destroy the cartridge. Another thing to be aware of is that if the cartridge is of the type where there's a turn over knob protruding from the front of the pickup head with LP and 78 marked on a flag, then this type will ruin your stereo records, regardless of it being set to LP.

[Techman]

Just checking out your first post 'properly' - typical of me

I see that the old mains lead has already been cut off short, so a lot of what I said regarding it isn't relevant, but may be useful info to another reader in the future - hopefully!

You're now going to have to fit some sort of cord grip to the new cable to anchor it to the inside of the cabinet as it's now a 'modification' and will need it to be safe, and you're now responsible for that by fitting a new cable.