UK Vintage Radio Repair and Restoration Discussion Forum

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-   -   Hitachi Model P-27FM (https://www.vintage-radio.net/forum/showthread.php?t=160629)

G8vsjDave 17th Oct 2019 5:46 pm

Hitachi Model P-27FM
 
Hi all. Iím a retired electronic engineer with a long term interest in anything related to television. I worked in the TV development labs at Rank Bush Murphy for a few years back in the early seventies before going into industrial electronics and later, systems. I have been following this forum for some time while looking for an old television to have a go at renovating it. I have renovated a few old transistor radios, but they were largely cosmetic.
While I was on holiday this year, my daughter phoned to tell me she had found an old television that had been in someoneís attic for the last thirty years. Her next statement floored me - ďit works, they plugged it inĒ. I really MUST have a word with my daughter.
On my return from holiday I was presented with a Hitachi Model P-27FM that looked in sorry state. The case cleaned up quite nicely, albeit a bit yellow, and today I switched it on for the first time.
There was no rustling of EHT, but after a few seconds a noisy raster appeared, I didnít have an aerial, but I turned the tuning dial and much to my surprise I had a very noisy picture of my front gate from my security camera which I donít understand at all. I can only think it is being radiated somehow from the recorder which is nearby. The other odd thing is that this Ďfront gateí signal does not seem to be picked up from the aerial socket Ė Itís there over most of the tuning range, and it doesnít make any difference if I connect an aerial or not. I then connected a Freeview box and attempted to tune to it without success.
I donít think the tuner is working properly because I canít find any sign of the Freeview box. The tuning voltage pin is changing as I adjust the tuning, and the V+ supply to the tuner is only about 10.4 volts. I assume it should be 12 volts. Oh yes, the speaker is open circuit.
Could I please ask if anyone could post a circuit diagram or give me a link to one.
Thanks for your time in reading this.
Dave

Restoration73 17th Oct 2019 6:22 pm

Re: Hitachi Model P-27FM
 
Hi Dave

PM your address details and I can post to you.

Tony

AJSmith625 17th Oct 2019 6:34 pm

Re: Hitachi Model P-27FM
 
Hello Dave, can't explain how you are getting a picture from your security camera. The only thing that does come to mind as you said, is some sort of radiation from the recorder box, possibly around 39.5 mHz IF frequency. Are you sure your Freeview box has a UHF signal output? Many modern boxes just have UHF loop through to pass the UHF signals on to other equipment such as a dvd recorder etc. If this is the case the audio/video outputs from the scart socket would need to be fed into a seperate UHF modulator. An old VHS video recorder is useful for this purpose. Otherwise great little mono portables I have a P20. They were built to last.

Alan.

Maarten 17th Oct 2019 10:55 pm

Re: Hitachi Model P-27FM
 
Some security cameras have a built in modulator.

G8vsjDave 18th Oct 2019 11:57 am

Re: Hitachi Model P-27FM
 
Thank you Tony, PM sent.

Alan, I think you are right. I connected a short wire to the IF input and got a much stronger signal from my Security recorder. These things must be very dirty at RF.
I hooked up my old JVC VCR and you are also right about my freeview box. RF from the VCR works fine.
Maarten - No, the camera is a simple PCB camera from our friends in China, but I have to say the performance at night is staggering.

For some unknown reason the 1Amp fuse went O/C. I replaced it and all is fine.

Dave

AJSmith625 18th Oct 2019 3:46 pm

Re: Hitachi Model P-27FM
 
The odd fuse popping off for no apparent reason was not uncommon on all these Hitachi sets. Don't be tempted to fit higher values. I put it down in the end to the fuse wire becoming 'tired'. Just fit a replacement, check there are no loose connections in the mains plug and all should be ok.

Alan.

G8vsjDave 20th Oct 2019 10:47 am

Re: Hitachi Model P-27FM
 
Thanks to Restoration73 for sending a copy of the circuit. I ran into a problem when I tried to adjust the picture centring magnets on the scan soils - they were missing. There is evidence in the grime on the scan coils that they were once there but there is no sign of them having 'dropped off' so it looks like they were deliberately removed at some time - WHY?. The scan is way off centre and turning the set through the earth's magnetic field did not help. I have put a post in the 'WANTED' section.
Dave

AJSmith625 20th Oct 2019 3:59 pm

Re: Hitachi Model P-27FM
 
Hello Dave, that is most unusual for these rings to be missing. I cannot imagine a tv set from a well known Japanese manufacturer ever passing quality control and leaving the factory in that condition. I have just had the back off my P-20, which although is probably a little older than your set, the 2 shift rings are there. They are brass coloured metallic rings, obviously not brass though and are clipped into 3 plastic lugs at the rear of the scan coil assembly. The only thing I can suggest is if you can get hold of one of those cheap Chinese 5.5 inch mono tv sets from a car boot sale and see if the rings from one of these may do.

Alan.

G8vsjDave 23rd Oct 2019 6:08 pm

Re: Hitachi Model P-27FM
 
3 Attachment(s)
Well, good progress is being made. I removed all the electronics and CRT and cleaned the case in a bath of warm slightly soapy water. The use of an old toothbrush and elbow grease worked wonders.
I borrowed the centreing rings from my old 9 inch video monitor to get the picture centred(ish), tweaked the frame linearity, and this is the result. Not perfect, but getting there. The next job is to visit the local car boot sale and find a freeview box. The attached pictures are from a pre-recorded VHS tape. Three guesses which one.
My thanks for all the help and advice.
Dave

AJSmith625 23rd Oct 2019 10:59 pm

Re: Hitachi Model P-27FM
 
Looking good, glad to see you found a solution.

Alan.

Richard_FM 23rd Oct 2019 11:09 pm

Re: Hitachi Model P-27FM
 
Quote:

Originally Posted by G8vsjDave (Post 1185811)
Well, good progress is being made. I removed all the electronics and CRT and cleaned the case in a bath of warm slightly soapy water. The use of an old toothbrush and elbow grease worked wonders.
I borrowed the centreing rings from my old 9 inch video monitor to get the picture centred(ish), tweaked the frame linearity, and this is the result. Not perfect, but getting there. The next job is to visit the local car boot sale and find a freeview box. The attached pictures are from a pre-recorded VHS tape. Three guesses which one.
My thanks for all the help and advice.
Dave

Looks like Andrew Emerson presenting The History Of The Testcard, with guest George Hersee, & mercilessly poked fun at on TV Offal.

G8vsjDave 24th Oct 2019 2:14 pm

Re: Hitachi Model P-27FM
 
Full marks Richard

Dave

Welsh Anorak 24th Oct 2019 4:24 pm

Re: Hitachi Model P-27FM
 
As you probably know there aren't many Freeview boxes with a built in modulator. If you can get one it will save you using a VCR as well.
There are a few about. The Labgear FV400 (not the 300) has one, as does the Goodmans/Alba that was given out as part of the digital switch-over. This latter might need capacitors in the power supply but that's an easy job. If you're lucky you might find a Ferguson (Sagem) 'Top-up TV' box. This has both a modulator and a hard drive so you can record the test card to your heart's content!
In all cases make sure you get the remote control.


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