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 1948 HMV 178E record player
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 Return to top of page · Post #: 1 · Written at 2:16:41 PM on 3 May 2012.
New2radio's Gravatar
 Location: Brisbane, QLD
 Member since 5 January 2009
 Member #: 410
 Postcount: 61

I recently bought myself a 1948 HMV 178E record player which I've restored cosmetically, but as I know NOTHING about electronics, I was hoping someone might be able to guide me as to the parts I'll have to buy to complete the restoration.
This is the record player in question, viewing the turntable area.

Image Link

And this is a view of the underside of the motor board.

Image Link

It's a pretty simple layout, and after cleaning & lubricating the motor, it seems to run quite well, although I think replacing the rubber sleeve that drives the turntable (rear left) should make it run a little quieter.
The pick-up itself appears to be working properly too, as wiring it directly into an external amp produces good volume.
However, with the player together and wired into a radio, the volume is fairly low, which I'm guessing has something to do with the old wax capacitors(?) that are present.
I'm pretty handy with a soldering iron, and as there seems to be only 3 items that will need replacing, I'm hoping this might be a good project for a complete novice to get his feet wet on electronically.
What I really need to know is what values/voltage I need to get to replace what's there, and where to obtain them.
I'm assuming these are all capacitors, so please correct me if I'm wrong Smile

The first one is small and has .0005 MF printed on it.
The other numbers I assume are just suppliers part or catalogue numbers and are of no use in 2012.

Image Link


The next 2 are huge & sit above the motor, visible when the turntable is removed, and I dont think I've seen capacitors so big before.
One has the value 1.3 MF +/- 10%, and the other is 1.1 MF +/- 10%.
I havent checked how these are wired, but I'm guessing the run in parallel, making a total value of 2.4 MF.
Do they even make them this big anymore lol.

Image Link


Ideally, I'd like to "stuff" the 2 large capacitors with the replacements, just to retain the original appearence when the turntable is removed, but I might be getting in over my head, so I'll cross that bridge once I've got the correct replacements in my hands.
So can anyone tell me exactly what I have to order & where I can get them?

Any help will be greatly appreciated.


 
 Return to top of page · Post #: 2 · Written at 4:30:05 PM on 3 May 2012.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 3972

From a safety viewpoint, I don't know if I'd use the term "getting feet wet" in association with electronics. Wink

You should definitely replace those capacitors on age basis alone.

EVATCO in QLD can supply you with:

1.0uF/630v polyester (yellow)

.0005μF is 500pF. They have 500v silver mica caps in that range.

Apart from dud capacitors, the attenuated signal may be caused by a number of things, including:

* the rubber suspension in the pickup head gone hard and non-pliable

* impedance mismatch between pickup output and amplifier input

* cold/dry solder joint or bad connection in pickup head

* high resistance in the cable between pickup and amp.


http://www.evatco.com.au/webcat1p12.htm.






 
 Return to top of page · Post #: 3 · Written at 3:15:52 PM on 6 May 2012.
Brad's avatar
 Administrator
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 4375

Capacitors in vintage equipment can come much larger, usually in metal cans and sit on top of the chassis. At one time they had to be physically large to get the required capacities. Modern materials and manufacturing techniques has brought physical size down. At times there were actually two capacitors inside the same package with three terminals, one to each capacitor and a common negative.


‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
Brad.

A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 4 · Written at 3:30:34 PM on 6 May 2012.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 3972

At times there were actually two capacitors inside the same package with three terminals, one to each capacitor and a common negative.

.... and more. My 1959 Hammond organ has 4 in the one can:

4uF/100
30uF/400
20uF/400
20uF/400

There may be instances of more than 4 in a can, but I haven't come across one personally.


 
 Return to top of page · Post #: 5 · Written at 3:40:30 PM on 6 May 2012.
Brad's avatar
 Administrator
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 4375

Haven't heard of four before though there must be a fair reason as to why more than one would get shoved into a single space like that. Cheaper to manufacture, making all to conform to the same electrical tolerances?


‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
Brad.

A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 6 · Written at 5:03:49 PM on 6 May 2012.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 3972

From the manufacturing aspect I'd guess that efficiency, and thus cost, would be a major factor along with a smaller inventory. From the user aspect, I'd guess the multi-cap's small footprint would be a factor.

Back in the day, Hammond made a lot of its own components, or jobbed it out locally. Although you can still get various 4-in-a-can combos (e.g. Evatco sells a 40/20/20/20 500v), this particular combination is unavailable so I have a spare which I am going to re-stuff with modern caps.


 
 Return to top of page · Post #: 7 · Written at 1:16:41 PM on 4 June 2012.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 2729

I don't see a full circuit for this in AORSM's...it might be there? It shows a volume control on a transformer from the magnetic PU.

Basically if the rectifier is a 5Y3 I would tend to use electrolytic caps of no less than 500V and just buy 630VDC ones to replace the papers.

If someone has a circuit & parts list that would be handy. Replace all of the electrolytics bearing in mind that any on cathodes, will not be 500V.

Any capacitors on the mains, should be of the mains "Approved" type or "motor run' if they are big.

TV's had multi, chassis mount caps as did some radios. (Old ones rarely more than two)

If you look at the base & side there is a reference to "triangle", "Half circle", "square", etc. And these are the positives of each electrolytic. They may not be all of the same voltage and may not be original.

Marc


 
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