French Miracle 510 1937 too many valves?

[Wishiknewmore]

Hello
I have bought yet another wooden box from a French car boot!
I have done some research and it's either a Miracle 510 (96-8) http://www.radiomuseum.org/r/radio_lyon_96_8.html
Or it's a Miracle Universel
https://www.doctsf.com/grandlivre/fi...ef=9019&ori=ps
But either way the fitted valves don't quite comply
The fitted valves are, 80,6B7,42,42,and an unmarked (see picture). This would agree with the 96-8 except it should only have 4 valves (an extra 42)
The Universel's line up is 6E8,EBF2,6C6,42.5Y3GB
Any wise words, thoughts or suggestions?
My current plan is to identify "that cap" and replace, find some replacement electrolytes(and replace if high load on limiter),replace the mains lead and power up via a lamp limiter.....is this reasonable or is there a better approach?
One other question that keeps haunting me is the voltage ratings on the non electrolytes they are rated at 1500v and in the past I have used blue ceramic disc rated at 2KV, could I/ should I be using yellow polyester at 630v? Do I need 1500v?
Many thanks again
Philip

[Nuvistor]

The 1500 VW capacitors must have been chosen for a good reason, if it was for safety reasons perhaps X or Y type capacitors should be the replacements, if across the primary of a sound output transformer it may require a high working voltage due to transients.

You will need to study the circuit to decide why 1500VW was chosen and replace with a suitably rated type.

[HamishBoxer]

Looks like French version of a Philco.that cap should be easy enough to find connected to the base of the 42 o/put valve(s).

[Boater Sam]

Test the transformers on ohms first?
If the HT is very high, which I would doubt, then 1500v may be sensible but I have French sets with 220v HT and they used 1500v glass caps for no good reason.
If any are as isolation for the likes of aerial or gram sockets then type Y. Any across the mains, type X. On the output valve anode, especially across the output transformer primary, then yes, 1500v is good. Types X and Y are not a good idea across transformers, just good high voltage ones.
The unknown looks like an output tetrode or pentode. Has it provision for a gram deck, hence the push pull output with two 42s?
Looks very interesting tidy set, does it have the French favourite coil pack in the front end?

[ms660]

The unknown valve might be a 6E8 which is a triode hexode, there's no osc/mixer with the other valves fitted. A full photo of the unknown valve might confirm either way.

Lawrence.

[PJL]

I am not convinced the 2x 42 is correct. If it's pp it should have a connection from each anode (pin 2) to the output to.

[Wishiknewmore]

Lawrence
Please find better pictures of the unknown/unmarked valve

Boater Sam
Yes it has a PU input for a gram
Thanks for info on caps. I will get my head around these things eventually
However, I don't know enough to know what you mean by "French favourite coil pack"

Nuvistor
Thanks for info, unfortunately I haven't found correct circuit yet.

HamishBoxer
Any ideas of which Philco it might be similar to, so I perhaps find and use that circuit?

Thanks everybody, this is the oldest set I have so far attempted and somehow it's just a little more daunting!

Philip

[ms660]

Thanks for posting the photo's up, that valve has a UX7 base so my current thought now is a 6A7, you can see that g3 and g5 are strapped together in the second photo so I would say it's a pentagrid mixer.

See what the others think.

Lawrence.

[PJL]

And there is a transformer added which needs investigation. I would not switch it on before you have drawn out the circuit.

[Wishiknewmore]

Would it be therefore safe to assume that my radio is neither of the ones I thought , as the valve bases and number of valves don't correspond to either model?
Does the valve line up as fitted look like a plausible configuration ?
Philip

[Wishiknewmore]

PJL
Yes I have noticed that
Forgive my ignorance,but I am not sure that it is a transformer as it has only two wires
I seems to have been put in series between the main transformer and the output transformer perhaps at the same time as a replacement 16 uF capacitor was fitted, by the marks and holes in the chassis there MAY have been a previous item fitted
Could it be a form of choke?
Philip

[ms660]

Originally Posted by Wishiknewmore

Would it be therefore safe to assume that my radio is neither of the ones I thought , as the valve bases and number of valves don't correspond to either model?
Does the valve line up as fitted look like a plausible configuration ?
Philip

The two 42's...maybe one's an AF amp and one's the audio output, or both are push pull...but what valve would be the splitter/inverter, check what the anode connections of both 42's are connected to, at least one of them should be connected to the sound output transformer that's mounted on the loudspeaker.

The lump of copper and iron on the chassis underneath, looks at first glance like a choke but you need to check how many wires are connected to it to try and confirm what it is.

EDIT: Post crossed.

Lawrence.

[ms660]

The "choke"...I can't make out exactly which tags on the UX4 valve socket are the two filament tags but it looks like the "choke" is connected to one of them via one the transformers filament supply tags, if that's the case and it only has two wires then it must be a choke, rigged up as a choke input filter maybe, can't see any connection for a pi filter but having said that it's difficult to tell from the photo.

Lawrence.

[Boater Sam]

French sets such as Schneider use a coil pack which is wrapped around the wave change which contains all the aerial and oscillator coils as a module.
They tend to be reliable which is just as well as they are a terror to work on.

[Wishiknewmore]

I have investigated further
There is indeed a connection from the anode (pin 2) on both 42 valves to the output transformer and pin 3 on each in also linked as is pin 5...does that make sense?
Does this make it a push pull set up?
There is also a 0.025MF capacitor connected to the pin 4 on both, is this the "that cap" that I should change?
I have some 473 1kv ceramic disc capacitors, if I use them in parallel will this be a suitable replacement?

Boater Sam ...yes now I understand about the coil pack...no this one doesn't but I have another in the queue that does, but the shaft is seized solid! I may need to take that apart which could be it's death knell.

[ms660]

Do the two anodes of the two 42's connect to two separate tags on the sound output transformer?

Try and trace where the two capacitors are connected to that each have one end connected to pin4 of each 42 valve.

Yes the capacitors connected to pin 4 of each 42 valve. will most likely be the grid coupling capacitors.

If it is push pull then it's possible that it might be using one half of the output stage as the phase inverter.

Lawrence.

[HamishBoxer]

There are a few I think Philco,s with p/pull using 2 x 42 valves but not sure which model mine is if I can get to it and check the model.

Nobody else is supporting me on might be Philco though.Of course I could be way out.

Mine is a Philco 582 but it is single ended o/put 42.

[Wishiknewmore]

I forgot about the 'choke'
This is in series with the second pin from the left on the transformer,which in turn appears to be linked to the first terminal which is connected to pin one on the UX4 ( 80 rectifier) the choke then connects to the yellow wire that goes to the output transformer
On the output transformer side of the choke there is a 16 uF capacitor to ground (this is a replacement at some time in the past)

Does it sound like this "choke" should be there?

Yours gratefully...Philip

[Wishiknewmore]

Lawrence
The two anodes do go to different tags on the output transformer, one is the green wire and one is blue as on one of the last pics
I got a bit stuck tracing the connections to the caps, the wires disappeared up into what I believe are tuning cans
I shall have another go tomorrow
Thanks again
Philip

[Tractorfan]

Hi,
Please forgive me if I'm stating the very, very obvious, but do check that the mains voltage selector is set to 230/240 volts. Because when these sets were common, the national line voltage in France was 110 volts, and a lot of sets were pensioned off with their selectors set to that voltage.
In my twelve years here I've seen a few burnt out appliances that were dug out of retirement and plugged in with the resulting loss of magic smoke!
Step down autotransformers are very common here to run old equipment on modern mains.
Cheers, Pete.