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 Schematic wanted for Hotpoint P64ME
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 Return to top of page · Post #: 1 · Written at 8:03:56 PM on 23 February 2017.
JamieLee's Gravatar
 Location: Clare, SA
 Member since 27 March 2016
 Member #: 1894
 Postcount: 508

I picked one of these up for $25 on Gumtree and currently doing a recap. I haven't tried plugging it in yet, will wait until re-capped. Everything is there, just some yellowish discolouration on the cabinet, any clues on how to clean it up are very welcome. I'm hoping it works well after re-cap and resistor check. Lot's of desiccated spiders cleaned out, apart from that it seems good, I just can't seem to find a schematic anywhere (usual Kevin Chant, Radio Museum etc) If anybody is able to help, I would really appreciate!


 
 Return to top of page · Post #: 2 · Written at 9:51:34 PM on 23 February 2017.
Brad's avatar
 Administrator
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 6573

If it is thermoplastic then whitening it is next to impossible. The plastics of the time were not good, even from quality manufacturers like AWA. Even modern plastics don't like UV light - check a 10 year old washing machine dashboard for details. It'll have been white when new and now yellow.

The best one can do is give the cabinet a good scrub in warm soapy water to remove dirt and grime. If originality is not a concern you could paint the cabinet but doing this is not easy to reverse either, when originality does become a concern.


‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 3 · Written at 11:26:54 PM on 23 February 2017.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 6172

Schematic and notes emailed to you.

As for yellowing of plastics, I have successfully re-whitened modern ABS plastic with peroxide hair bleaching cream and sunlight. My understanding of the chemistry involved is that the yellowing is the result of bromine flame retardant in the ABS reacting to heat and UV over time. Apparently the hydrogen released from the peroxide cream reverses the process.

However, I don't think this would work on older plastics. I think we just have to consider that the patina of vintage.


 
 Return to top of page · Post #: 4 · Written at 12:01:33 AM on 24 February 2017.
Vintage Pete's avatar
 Location: Albury, NSW
 Member since 1 May 2016
 Member #: 1919
 Postcount: 2045

On vintage motorcycles plastics we heat the yellowing up with a hair dryer to re-activate the chemistry and then we just re polish it.

If it is so bad that it has turned white and flakey, we heat it up with a hair dryer and scratch it off in straigh lines and then re polish using wet and dry 800, 1200, etc and then buffing compound.


 
 Return to top of page · Post #: 5 · Written at 12:28:52 AM on 24 February 2017.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 6172

I have successfully restored the case of my maroon Krielser Duplex, which had suffered sun or heat damage on one end making it a whitish-pink shade, first by rubbing it back with grades of wet and dry and then recovered the colour and shine with Autosol liquid metal polish.

Using the same process, I even managed to "unfrost" the plastic dial cover so that it is now completely transparent. I took a gamble on that part and won.

That radio case now looks like new.

I guess that process could be used to remove yellowing, too. Worth a try on a write-off case first.


 
 Return to top of page · Post #: 6 · Written at 1:36:09 AM on 24 February 2017.
Vintage Pete's avatar
 Location: Albury, NSW
 Member since 1 May 2016
 Member #: 1919
 Postcount: 2045

Not all plastics have colour pigment all the way through so best to check that out.

On vintage Japanese motorcycles the plastics are always faded and scratch and this is how we repair them because you cant buy new ones. Wet and dry and work your way up the grades until its spotles,go up to about 2000 grit , and then polish with car polishing compond then a fine polish. I recently did this process with a green plastic Ranchero radio that was so badly scratch it looked like a kid had attack it with a fork. Now there is not a mark on it and it looks like new.

It's time consuming but well worth it. But yellowing is harder to get rid of than scratches , if you get time have a look on the internet about restoring plastics some guys out there really know their stuff.

PS: 2000 grit or above can not be bought at the hardware you need Auto One or Repco.


 
 Return to top of page · Post #: 7 · Written at 9:39:59 AM on 24 February 2017.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4506

One of the other things that destroys early plastics, like coil formers, is themselves. The cellulose in earlier times is a Nitro cellulose & it starts decomposing from day one: That's where the brown stain comes from (Nitrates). Many plastics like the stuff they made "Barbi Dolls" out of, create Hydrochloric acid as a decomposition product and it is the catalyst for further decomposition.

This is becoming a serious issue for those trying to conserve art works made of plastics.


 
 Return to top of page · Post #: 8 · Written at 10:52:34 AM on 24 February 2017.
Vintage Pete's avatar
 Location: Albury, NSW
 Member since 1 May 2016
 Member #: 1919
 Postcount: 2045

Nitrocellulose never cures , So its constantly changing with temperatures. Even car finishes that were done in nitrocellulose can easily be re activated and removed
after years of being on the car.

Terrible finish for a car,but it was used for years for its ability to mix paint with so many colours could be achieved.

As for furniture Nitro gives a wonderful finish that in high gloss no other can match in many ways. Plus it can be toned with dyes or even paint. But yes it breaks down and cracks and yellows with time ,sometimes it takes 2 years other times it takes 30 years, but it can be re activated and repaired and made to appear original again,which no poly can do.

I have a 57 year old cabinet that was finished in nitro in 1960 and there is not a crack in it.
So impossible to put a time on cracking ,which we call checking.


 
 Return to top of page · Post #: 9 · Written at 8:44:01 PM on 24 February 2017.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 6172

BTW: The Hotpoint P64MEX version is featured in the Vintage Radio section of the February 2017 issue of Silicon Chip.


 
 Return to top of page · Post #: 10 · Written at 11:20:58 PM on 24 February 2017.
JamieLee's Gravatar
 Location: Clare, SA
 Member since 27 March 2016
 Member #: 1894
 Postcount: 508

Thank you all, very interesting indeed. The radio sounds awesome now after a recap, new earthed cloth covered power cord, hole in the speaker repaired with aquadhere and tissue paper, new speaker grille cloth (my wife had some perfect white material, new dial lamps, a very thorough clean (it was full of dead spiders and their doings plus one very alive white tip which got vacuumed!), and a volume knob, (not original, but suitable) It actually looks nice after a scrub in the sink with warm soapy water and we are now enjoying our evening listening to it. Thank you very much for your comments! Cheers!

Hotpoint P53ME Radio


 
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