Reps JC20 Reel to Reel

[Starlight 1]

Originally Posted by DMcMahon

This appears to be C36, although the schematic does not show it connecting to the fuse.

Cannot quite see from the photo (my eyes are not as keen as Grahams) but is there a wire connecting to the Bulgin mains connector where the broken end of C36 connects to ? this wire should connect to earth as per the schematic.

David

Yes it was a Earth.

[Starlight 1]

I don't like the thought of paying £18 for a plug which doesn't work so I have fitted a kettle plug socket - see photo, as safety must come first. Have added
an extra photo for anyone interested in seeing the underside.

[Techman]

You've done the right thing, however.....

You've fitted that earth eyelet solder tag under that bolt, but does it connect to earth?

It looks to me like it goes nowhere!

Meter it out to check continuity to chassis ground.

The old socket enabled it to connect directly to the chassis at the rear.

As you said yourself - safety must come first!

[DMcMahon]

Measured a large Bulgin chassis connector at around 26.75mm for the body that goes through the chassis hole. I now assume the hole size referenced at Post 4 was for the hole (opening) on the pin side, which on mine is a nominal 23mm. If the hole size referenced at Post 4 was for the chassis hole, then that is confusing, maybe 2 size variants of the larger Bulgin (seems unlikely) or not a Bulgin connector (certainly looks like a Bulgin). Width of mine at the front is around 38mm and around 33mm for the mounting holes. It has a square keyway.

The mini Bulgin chassis connector is nearly 19mm across the threads (single large nut secured version) and around 23mm wide on front face with around 15mm opening at pins. It has a curved/semi-round keyway.

David

[Techman]

It may well be that the shaft of the bolt just touches the chassis metalwork as it passes through the hole, but that's a very unreliable connection - a meter may show continuity for the moment, but a proper connection should be made. This is the whole trouble with modifications to mains inputs, which is strictly speaking illegal, although thousands of people do it, and which is one reason that I'm personally against inexperienced people doing it. However, in this instance it was the best thing to do so long as it's done safely and doesn't make the unit more dangerous than it was originally. Hopefully the OP can confirm how that earth tag connects properly to the chassis.

[DMcMahon]

Originally Posted by Starlight 1

I don't like the thought of paying £18 for a plug which doesn't work so I have fitted a kettle plug socket - see photo, as safety must come first. Have added
an extra photo for anyone interested in seeing the underside.

Well done, doubly check and confirm the integrity of the earth connection as per Techman's inputs.

It is good to see the insides, it looks well built/engineered.

David

[Starlight 1]

Maybe I used the wrong name for the lead and plug but it only fits one way round and I have put a 2 amp fuse in the wall socket end and the earth pin on the board has 2 eyelets one from centre pin and one from bottom pin just to make sure I have a good earth when I put it back on to the chassis.

[Station X]

Personally I'd use a separate bolt to connect the tag on the earth lead to the chassis and not rely on one of the bolts holding the socket to the chassis.

[Starlight 1]

Originally Posted by Station X

Personally I'd use a separate bolt to connect the tag on the earth lead to the chassis and not rely on one of the bolts holding the socket to the chassis.

One eyelet do have a separate bolt for the chassis .

[Starlight 1]

I look at all posts again , its back in the case and I test on Sunday as its now dark here. This is from the reel side under the cover. Les

[DMcMahon]

Les - Something to be aware of :-

The black 0.1uF 400VDC capacitor in Post # 10 is a Hunts paper capacitor (a Moldseal I think), these old capacitors (and other makes) are notoriously known to be electrically leaky and also known to crack.

This type of capacitor when electrically leaky can cause various problems when used as a grid coupling capacitor as per this linked Thread.

https://www.vintage-radio.net/forum/...ad.php?t=73399

Potentially serious for the grid coupling capacitor at the output valve (which drives the loudspeaker), in your case the capacitor is C19, also listed as a 0.1uF

This connects the anode output of the EF86 valve V3 (pin 6) through to the control grid input (pin 2) of the EL 84 (V4) output valve via resistor R25 (2.2kOhms).

If you have a test meter and can safely measure the voltage, would strongly recommend that you check for +ve DC voltage at R25 wrt (with respect to) ground, there should be virtually no +ve voltage, if C19 is leaky then there could be a lot of +ve voltage at R25.

David

[Starlight 1]

I did see this last post till after the test only see if it power up with a test light 40v on for 10 min every thing look ok will it be ok to test the rest.

[DMcMahon]

Good to see you are using a lamp limiter, I assume you got the information from "Series Lamp Limiter" :-

https://www.vintage-radio.com/projec...p-limiter.html

The lamp limiter is referenced at the start of "Applying Power for the First Time" :-

https://www.vintage-radio.com/repair...ing-power.html

This procedure is written for Radios but apart from any Radio specific references generally equally applies to a valve tape recorder.

Is the bottom unit some sort of variable AC (such as a Variac), I guess it must be if you are able to adjust/reduce the mains voltage down to 40V

Yes I would continue on adjusting the mains voltage up to 240V, making sure the lamp limiter bulb stays dim.

At the "HT" section of the "Applying Power for the First Time" it references measuring the voltage across the control grid resistor of the output valve, this is the R25 I referenced.

If you do not have a test meter, you could try and identify/locate C19 and take a photo to see what type of capacitor it is, it possibly could be a type that does not go leaky.

David

[DMcMahon]

Originally Posted by Station X

I've blown up the picture which shows a wire connected to a "floating" solder tag. I assume the tag was bolted to the chassis, but was unbolted when the player was dismantled?

I can clearly see the earth wire on my old PC monitor but on my new laptop (which has a higher video resolution spec I think) struggle to see it.

David

[Starlight 1]

I don't understand electronics so that's why I don't play with them Have now taken it to 240v no limiters as the motors will not run with it on No strange sounds or paculiar smells
Both motors run forward and reverse Shall I try tape just out of curiosity? I do appreciate all the posts and help I am getting from this forum

[DMcMahon]

Yes try playing a tape.

David

[Starlight 1]

I have tried a tape for 2/3 mins twisted some knobs still no sound so I tried
one of my tapes from my home recording studio and it sounds fine and the quality was good

[Station X]

I strongly suggest that you check the voltage on V4 control grid or replace C19. If you don't you may well find that smoke escapes from your recorder and it won't be easy to put it back again.

[Starlight 1]

Originally Posted by Station X

I strongly suggest that you check the voltage on V4 control grid or replace C19. If you don't you may well find that smoke escapes from your recorder and it won't be easy to put it back again.

It will not be used any more till I can get it sent to a repair shop for a full check up and any work to be done. Les

[DMcMahon]

The main concern is that if C19 is leaky (or subsequently becomes leaky in the future) then if a large DC voltage gets onto the output valve control grid it could kill the valve (easily replaceable but not cheap) and worse still could wreck the output transformer (identified as L2 on the schematic) which would be a disaster as it then would be very difficult to source a suitable replacement.

This is a worst case scenario but is possible.

David