Newbie Needs Help With Project. Philips radiogram H4X75BT.

[magician]

I was given a Philips radiogram H4X75BT and would like to get it working. This will be my first restoration project.

The initial electronics I will replace consist of some resistors, capacitors, transformers, and transistors.

I have included pictures if someone can recommend alternative replacement parts otherwise I have a few questions.

Would this 6.3V 4A transformer be a suitable replacement for the current 6.3V 3A transformer? https://www.mojotone.com/amp-parts/P...er-transformer

Is it okay to replace the capacitors with new capacitors that have equivalent ratings?

I can't read any of the markings on the transistors, is there a way to tell what the appropriate replacement would be?

I'm not sure about the readings on the large blue capacitors (MFD 500, VW 100)?

There is also a smaller brown transformer which I am not sure what it's ratings are.

Any help would be much appreciated.

[Station X]

Hello and welcome to the forums.

That obviously isn't the original amplifier. The Veroboard and using a heater transformer to power transistors is a dead giveaway.

No service information will be available so you'll have to reverse engineer the circuit.

Why do you want to change the transformer and transistors? Have you tested them?

[Station X]

Some info here:-

https://www.radiomuseum.org/r/philips_h4x75bt.html

Have all the electronics been ripped out? There would have been a radio with four valves, the audio section of which would have served as an amp for the record deck.

I wonder if this is an attempt to convert a mono player to stereo?

['LIVEWIRE?']

My first thoughts are-if the amplifier is working, and producing decent quality sound, why replace anything? Basically, in any circuit, only known faulty components should be replaced.

[Graham G3ZVT]

Originally Posted by Station X

Some info here:-

https://www.radiomuseum.org/r/philips_h4x75bt.html

Have all the electronics been ripped out? There would have been a radio with four valves, the audio section of which would have served as an amp for the record deck.

I wonder if this is an attempt to convert a mono player to stereo?

I've just downloaded the circuit from radiomuseum Originally a hybrid 4 valve + 4 transistor battery/mains radiogram. 45v HT 6v LT with the 1.4v heaters in-series.

[Cobaltblue]

I am wondering if the original Radio is in place and all the additional equipment shown is just an LT and HT power supply to provide the LT and HT for the Battery Valves?

Original requirements are 6V and 45V the output is already transistorised as Graham has already mentioned.

Nice rare piece very few Hybrids like this around

Cheers

Mike T

[paulsherwin]

It's obviously been severely got at. If none of the original electronics survives, it would probably be better to junk all the manky old circuit boards and fit a modern power amp module and power supply. You can buy suitable modules from eBay sellers in China for a couple of dollars.

It appears to be pretty far gone though, unless you want to tackle it as a challenge.

Can you post a picture of anything that looks like valves/tubes?

[julie_m]

I can't see enough on that breadboard to make an amplifier, but a 6V/25mA regulated power supply is feasible. I think we need more pictures!

[Station X]

I've not looked at the circuits available from Radio Museum, but the description says this radiogram is battery powered. So did it have a battery powered turntable motor?

I'm coming round to the view that the Veroboard lash up was intended as some kind of battery eliminator.

[ms660]

Philips Service Notes (aka the manual) here:

https://elektrotanya.com/philips_h4x...wnload.html#dl

Lawrence.

[magician]

Thanks to everyone who has responded!

The original pictures that I posted (veroboard), I was not able to find anywhere in the service manual, so yes it makes sense that it is not original. I also cannot find anything that looks like batteries so maybe StationX is correct.

I have not tested any parts yet as I thought I should just replace as much as possible, but I now think I will start testing the different components and only replace what is necessary.

I know this is going to be a real challenge, (I've never attempted anything like this before) but it is such a beautiful radiogram and the box itself is in really good shape other than some chipped veneer on the side panels.

I have attached more photos, the first is before I took it all apart and the other 2 are closeups.

Of course anymore advise is much appreciated.

[Graham G3ZVT]

Thanks Lawrence. Obviously it was a battery only set, not battery/mains as I said.

The manual says the 6v battery was 4 X 1.5v cells but gives no further clue. 4X U2 probably, and the 6v runs the gram motor. There is a mod to change the suppression choke if the turntable runs slow.

What would be available for 45v? A No 455 battery looks too modern.

[Station X]

Originally Posted by magician

Thanks to everyone who has responded!

The original pictures that I posted (veroboard), I was not able to find anywhere in the service manual, so yes it makes sense that it is not original. I also cannot find anything that looks like batteries so maybe StationX is correct.

I have not tested any parts yet as I thought I should just replace as much as possible, but I now think I will start testing the different components and only replace what is necessary.

I know this is going to be a real challenge, (I've never attempted anything like this before) but it is such a beautiful radiogram and the box itself is in really good shape other than some chipped veneer on the side panels.

I have attached more photos, the first is before I took it all apart and the other 2 are closeups.

Of course anymore advice is much appreciated.

The original radio is there complete with valves. You might find that if you make up some batteries it will work. No need to bother about powering the turntable at this time.

Personally I suggest that you don't go in for Compulsive Component Changing (CCD), it could be a recipe for disaster.

Much useful information here:-

https://www.vintage-radio.com/repair...ion/index.html

A word of warning. Make sure you don't apply HT (High Tension) voltage to the valve filaments. They'll be instantly rendered useless.

[Graham G3ZVT]

Hi magician.
Suddenly, this has become a viable restoration project now we know nothing is missing.
The way it was powered by batteries and the use of valves and transistors is unusual for a radiogram, I have never seen anything quite like it.

There are multiple options for repairing or replacing the "battery eliminator" but if it was mine I would remove everything on that wooden baseboard plus the two large electrolytics, and restore the set to it's original state.

This may seem daunting to you, but if you look closely you should find there are only three connections made to the radiogram proper.

I would use 4 "D" cells in a holder for the 6V, and 5 regular 9V batteries wired in series in a cardboard box for the 45V. That battery will last a long time in that particular set, even without allowing for the fact that modern alkaline batteries have a far greater power density to what was available in the 1950s

[ms660]

What about the single cell (A1 in the schematic)?

Lawrence.

[Graham G3ZVT]

I don't know! a NiFe cell perhaps? I've arrowed it on the OPs photo.

[Maarten]

Likely an NiCd cell, usually called DEAC after the largest manufacturer back then.

In this case, it's used as a voltage stabiliser for the bias of the output stage. If it's defective, it can be replaced by an NiMH cell or by 2 diodes in series with an electrolytic across.

The chassis in this particular example was made some time after week 31 of 1957 at Philips Leuven, Belgium. The radiogramophone set itself was made some time after week 29 of 1958 in Eindhoven, The Netherlands. Leuven probably only produced chassis and radio-only sets while Eindhoven did the 'specials'. There's a large warehouse in Acht, near Eindhoven, where unfinished products and end products alike were stored for finishing, distribution and export. The chassis were likely transported in bulk by train, exempt from customs and tarrifs.

[donutty]

Ref: the smaller transformer.

I didn't know Leica made transformers!

[Maarten]

Well spotted, I only saw "Wetzlar" and thought "nice, 2 transformer factories in one city" (Philips being the other one). It makes sense; Leitz would have used low voltage lighting in their optical equipment and needed transformers for that, so why not make them themselves (the exact same reason Philips did, be it for their radio production).