Trying to restore a Columbia 357, help please.

[Scotorvm]

Guy's, I was wondering if someone could help me. This appears to be untouched apart from maybe replaced valves. Don't have a great deal og knowledge about radio restoration apart from youtube videos. Started dabbling during lockdown.

Have taken on a Columbia 357 to restore, purchased the data DVD from this site and following the data sheet 577 for the Marconiphone 264, a few issues it has are -

1. dial cord broken, I believe the pointer seized on the slider and the cord snapped, all the parts are present. Any tips in replacing would be appreciated, where the springs go, the position of the tuning capacitor and dial pointer etc..

2. When the radio was removed from the case a 1uF capacitor was lying adfrift from the radio, I think it fell out of an area, I have put it in a pic where I think it should be, but not sure where this solders onto.

3. Valves removed and stored safely, V1 - MX40, V2 - VMS4, these match the trader sheet info. V3 is an ever ready A23A I assume a replacement for MHD4, V4 not sure but maybe damaged, a slight rattle when tilted, in the data sheet it is MPT4, I tried to clean the dirt off but the label was removed to, I think it is Mullard only number left is Z8159, it is 5 pin with an additional screw cap on the side just above the pins. V5 is a Mazda UU5 which I think is a replacement for an MU12.

4. R28 appears to be a wire wound resistor, I can see the wire sticking out at one end, would a modern resistor be ok to replace this, could be hidden inside as the resistor is hollow.

5. I think there is also a box of caps located behind the resistor plate, hopefully this will be ok.

6. I have an external speaker which I was hoping to use, connecting to terminals ext. and LS on the speaker itself, the resistance of the speaker is 1.87k ohms, would this work? Also wondering what all the ports on the back of the set are for especially the ports that are selectable my moving a plug for AE, mains AE off and Earth.

Apologies for all the questions, just learning. Thanks.

[Station X]

Lot's of questions there. I'll endeavour to answer some of them.

Before replacing R28 check it with your meter on a resistance range. It may be OK.

It's highly likely that the capacitors in the box will be electrically leaky. You may have to restuff it.

Identify all the 1.0uF caps in the circuit and check which one is missing.

[Herald1360]

You've not picked an easy set to cut your restoration teeth on!

The loudspeaker is an energised field type with the electromagnet coil used also as the HT ripple filter inductor and it has a low impedance voice coil fed from a matching transformer in the output valve anode circuit. A high impedance horn speaker would not be at all suitable.

The capacitor block- sorry to depress you even further- probably full of leaky (as in low insulation resistance) paper dielectric capacitors. At least the Trader sheet provides details! It is a pain to extract and ditto to rebuild with new parts inside.

Various rear panel connections- AE (A on the circuit) is the aerial input, normally connected to a (long) wire strung up outdoors for best signal pickup. E is for earth, for connection to another wire going to an earth rod in the ground outdoors again. Mains AE is a dubious (safety wise) and useless (in today's world of noisy mains supplies) link via a capacitor from the aerial circuit direct to the mains input. Best to remove that capacitor and forget it, though you could replace it with a suitable Y- class mains suppression capacitor just to find out (relatively safely) just how noisy your mains supply is!

Usual recommendation is to learn on a much more recent ('50s or early '60s) "woody" set or two which will be far easier to work on whilst having many of the same basic problems to be fixed!

That said, if you're not too disheartened, there's plenty of help and advice here to enable you to have a go at what you've got and deal with specific problems as they arise.

A search in the forum will probably turn up threads on the restoration of the same set or at least the Marconi 264 variant.

Have fun, and take care- old radios can be just as lethal as pandemic viruses

[paulsherwin]

To reinforce Chris's comments, you are taking on a lot choosing a 1935 radio as a first restoration project - it's not impossible, but there will be an awful lot to learn. You should only attempt the job if you are certain you have the commitment to see it through.

You can't use your horn speaker with this radio. It's about a decade older and intended for use with the first generation of valved broadcast receivers which wouldn't have used an output transformer.

[Scotorvm]

Originally Posted by Station X

Lot's of questions there. I'll endeavour to answer some of them.

Before replacing R28 check it with your meter on a resistance range. It may be OK.

It's highly likely that the capacitors in the box will be electrically leaky. You may have to restuff it.

Identify all the 1.0uF caps in the circuit and check which one is missing.

Cheers Station X, will try and find the missing cap, the cap that is off is a big one and not a lot of places where it can hide, the value of it is way of measuring 4.16uF on the ESR. R28 is open circuit, R27 above it is 300ohm so my meter is working OK.

Thanks.

[Scotorvm]

Originally Posted by Herald1360

You've not picked an easy set to cut your restoration teeth on!

The loudspeaker is an energised field type with the electromagnet coil used also as the HT ripple filter inductor and it has a low impedance voice coil fed from a matching transformer in the output valve anode circuit. A high impedance horn speaker would not be at all suitable.

The capacitor block- sorry to depress you even further- probably full of leaky (as in low insulation resistance) paper dielectric capacitors. At least the Trader sheet provides details! It is a pain to extract and ditto to rebuild with new parts inside.

Various rear panel connections- AE (A on the circuit) is the aerial input, normally connected to a (long) wire strung up outdoors for best signal pickup. E is for earth, for connection to another wire going to an earth rod in the ground outdoors again. Mains AE is a dubious (safety wise) and useless (in today's world of noisy mains supplies) link via a capacitor from the aerial circuit direct to the mains input. Best to remove that capacitor and forget it, though you could replace it with a suitable Y- class mains suppression capacitor just to find out (relatively safely) just how noisy your mains supply is!

Usual recommendation is to learn on a much more recent ('50s or early '60s) "woody" set or two which will be far easier to work on whilst having many of the same basic problems to be fixed!

That said, if you're not too disheartened, there's plenty of help and advice here to enable you to have a go at what you've got and deal with specific problems as they arise.

A search in the forum will probably turn up threads on the restoration of the same set or at least the Marconi 264 variant.

Have fun, and take care- old radios can be just as lethal as pandemic viruses

Thanks Herald1360
I bought the speaker as I liked the look of it, hopefully find a use for it sometime. Thanks for info on the rear connections to, yes I did read somewhere the hidden caps are in a block of pitch, not looking forward to repairing that if I need to.

I have a safety isolating tranny supplying a Variac, I'm an Electrician with an HND Electrical/Electronic I know where to keep my fingers away from, famous last words , just never seen components as old as these. I've restored a Pye P75, working great, looking at an EKCO U243 just now. You're correct, these 50's sets seem a lot easier to work on

[PJL]

You will need to replace the capacitors in the block as they will all be leaky. It requires a great deal of patience and a methodical approach as all the wires to the block need to be unsoldered and carefully marked up so they can be put back together correctly.

It's a very ambitious project for beginner...

[Scotorvm]

Originally Posted by paulsherwin

To reinforce Chris's comments, you are taking on a lot choosing a 1935 radio as a first restoration project - it's not impossible, but there will be an awful lot to learn. You should only attempt the job if you are certain you have the commitment to see it through.

You can't use your horn speaker with this radio. It's about a decade older and intended for use with the first generation of valved broadcast receivers which wouldn't have used an output transformer.

Thanks Paul, I bought this radio as it looked like a nice set, the case in great condition, yes the speaker is 1920's, will try and find a set to suit, have been restoring old Roberts sets, PYE picnic sets, but this one seems more complicated, I won't rush it.

Comment appreciated

[Scotorvm]

Originally Posted by PJL

You will need to replace the capacitors in the block as they will all be leaky. It requires a great deal of patience and a methodical approach as all the wires to the block need to be unsoldered and carefully marked up so they can be put back together correctly.

It's a very ambitious project for beginner...

Thanks PJL, beginning to think I chose the wrong set now I will take this slow and hopefully update in the future.

[Scotorvm]

Moving back to this restore, have now ordered caps to try and tackle the pitch filled condenser block, have identified most of the wires coming out of the pitch, going to chop and join modern caps discretely, only issue is, as per my original post, when I removed the radio from the case a large 1uF cap fell out from the underside of the chasis, next to the resistor tray. It is 2" long and 1" in diameter, waxed at both ends.

Have examined the trader sheet 577 and there are no external caps of that size, the only 1UF caps are in the pitch condenser block.

Could this be an old replacement for a cap in the condenser block installed externally? The cap C15, I cannot see any wires leaving the resistor tray to the pitch block.

I think there was an older post on here by Fableglade in 2003 who successfully
achieved the condenser block cap workaround, not sure if the user is still active, any help / pics / tips / appreciated.

Thanks.

[Station X]

Just ignore the 1uF cap and wire the radio as per the service sheet.

[Scotorvm]

Originally Posted by Station X

Just ignore the 1uF cap and wire the radio as per the service sheet.

I will do Graham thanks.
Just confused why it would be rattling around in there, waiting on caps being delivered.

Cheers
Lee

[Scotorvm]

Almost finished the restoration, stations are tuning in, so getting there.
Went down the route of leaving the condenser block un-touched, cutting the wires coming from the block and running new wires from the points on the trader sheet diagram to modern caps.
A few out of value resistors changed, the decrease static POT on the rear was shot, fitted a modern POT while keeping the existing in place.
Case polished up nicely, small area on top I left un-touched to save the Columbia label.

The valves are -

1. Marconi MX40
2. VMS4??
3. Marconi MHD4
4. Marconi MPT4
5. Mazda UU5 equivalent to Marconi MU12

Question re valve 2 – VMS4, when I received this set all the grey metalised shielding paint was coming off, removed and painted with guitar screening paint, have continuity between the middle pin and the painted surface. Not sure if this valve is good, have no means to test it.

Would I be able to use any of the other 2 valves? Reading trader sheet 577, this valve is supposed to be a Marconi metallised VMS4, not sure if the metallised part is supposed to be coated externally or not.

The one labelled with black pen does not have an external coating. The top connector is the same. It has the Marconi red label on it.

The other valve I believe is NOS with box, but has the wrong top connector, it is clearly marked VMS4 and would probably be the best one to use. Would it work if I soldered a wire to the copper clip inside the aluminium cap and with a crimp on the end of the wire to be clamped by the top connector then put the aluminium cover over this?

Thanks guy’s.

[cathoderay57]

If it were me I would give them a try - probably the NOS (if indeed it is) would be your best bet using a modified top cap connection. However, a word of warning. As the original valve appears to have been metallised, the replacement being unscreened (I think the silvering is probably the getter not an internal screen) you might find the set oscillates and signals become unstable. You would then have to devise some means of screening the valve. Maybe some VMS4 were produced unscreened for sets with an external valve screening can. Cheers, Jerry

[vinrads]

When you come to doing the capacitor block be sure to take some pictures, also a good idea is to ID the wires with heat shrink sleeving it comes in loads of different colours just a small piece will do, done a few of these. I found you can leave one side connected and and bend the assembly out of the the way.

Well done with your efforts so far good luck with it, Mick.

[Scotorvm]

Originally Posted by cathoderay57

If it were me I would give them a try - probably the NOS (if indeed it is) would be your best bet using a modified top cap connection. However, a word of warning. As the original valve appears to have been metallised, the replacement being unscreened (I think the silvering is probably the getter not an internal screen) you might find the set oscillates and signals become unstable. You would then have to devise some means of screening the valve. Maybe some VMS4 were produced unscreened for sets with an external valve screening can. Cheers, Jerry

OK that's great, thanks Jerry, I will try them and see what happens, I bought the valve with the screw connector as NOS, not sure if the box is correct.

Forgot to mention and not sure if it was my setup, I'm in a cabin in the garden, with, loop aerial on top of a fence, fan heater going (-11 in Scotland), led lights, PC running etc.. stations tuning in seem to have another station in the background. Will move the set into the house and try there, it's a heavy bit of kit, beats going to the gym

Cheers
Lee

[Scotorvm]

Originally Posted by vinrads

When you come to doing the capacitor block be sure to take some pictures ,also a good idea is to id the wires with heat shrink sleeving it comes in loads of different colours just a small piece will do ,done a few of these I found you can leave one side connected and and bend the assembly out of the the way, well done with your efforts so far good luck with it , Mick.

Thanks Mick, I do take loads of pics to remind me of wiring points etc. It's easy to forget when you return to a project after 6 months. It's nice to hear others have restored these sets. When I cut the wires I labelled each with dymo tape, for future reference.

Those trader sheets are a godsend by the way, highlighting the capacitor connections in the pitch block

[Radio Wrangler]

Messing around with pitch-filled capacitor blocks can get very messy very fast.

You might want to consider making a replica block with modern capacitors inside it and no pitch at all involved. You can construct internal structures from plasticard and glue, or else from fibreglass sheet (raw printed circuit board material with all the copper etched off) and epoxy. An outer cover made of folded card with well-thinned black paint absorbed into it can look the part.

It depends how original you want the insides to look. Some people have gone so far that subsequent owners/restorers tried to change components only to find that the parts present were restuffed originals or replicas!

David

[Scotorvm]

Originally Posted by Radio Wrangler

Messing around with pitch-filled capacitor blocks can get very messy very fast.

You might want to consider making a replica block with modern capacitors inside it and no pitch at all involved. You can construct internal structures from plasticard and glue, or else from fibreglass sheet (raw printed circuit board material with all the copper etched off) and epoxy. An outer cover made of folded card with well-thinned black paint absorbed into it can look the part.

It depends how original you want the insides to look. Some people have gone so far that subsequent owners/restorers tried to change components only to find that the parts present were restuffed originals or replicas!

David

Thanks David
Yes, I agree with you, that would be the best way to continue, last time I etched a PCB was college in 1990
Don't have a lot of time just now and have been taking this set into work to progress on nightshift.

But great info for future reference

[PJL]

Freeze the capacitor block and the bitumen can be chipped out BUT do it outside or the splinters will thaw and make a real mess.