Sourcing Old Radio Parts

fraglerocks

Does anyone know where I could buy parts for an old radio off the internet. Basically, I want to email a wiring diagram and a few photos of the internals and them to come back to me with a price and lead time for the parts they'd recommend replacing.

watty

Doesn't work like that.

You have to know what you are doing and test the parts.

Then you replace the faulty ones.

http://www.radiomuseum.org/forum/replacing_old_capacitors.html

http://www.radiomuseum.org/forum/servicing_old_radios_useful_tips.html

An example
http://www.radiomuseum.org/r/hismasters_hmv1121hmv_112.html

fraglerocks

How ya Watty,

I was actually hoping someone else would do the running around for me and then once I got the parts I'd just take out the suspect parts and solder in the new!

I've never tested a capacitor in my life. Do they have to be removed from the circuit in order to test them? Is it the continuity test I use to check them or what? I'd prefer not to have to remove capacitors from the circuit to check them if there's nothing wrong with them in the first place. I only have a cheap little multimeter that I bought on ebay a while back so I don't think it will be any good for checking the capacitors. This is its spec:

- AC Current

- Range 20A, 200A, 400A

- Overload Protection : 400A on all ranges

- AC Voltage

- Range 450V

- Overload Protection : 450V AC/DC on all ranges

- DC Voltage

- Range 600V

- Overload Protection : 600V DC / Peak AC on all ranges

- Diode Test / Transistor P-N junction test

- Continuity test with buzzer sound while < 75 Ohm

- Resistance Measurement. 200K Ohm Range

- Overload Indication


It's turning out more complicated than I envisiged...or maybe I'm just lazy and don't want to spend weeks trying to source parts and getting it to work... Do you know anyone in the Mayo/Connacht area that I could just send it to to get it fixed as I think I'll probably do more harm than good? If I could get it up and running for €100-€150 I'd be happy.

watty

fraglerocks wrote: »

How ya Watty,

I was actually hoping someone else would do the running around for me and then once I got the parts I'd just take out the suspect parts and solder in the new!

Unfortunately not possible as while certain parts (wax paper capacitors or Hunts Mouldseal) are often faulty, they are not universally to be replaced. Other "random" faults can exist. The HMV1121 example had one unlikely capacitor faulty, all the ones usually needing replaced were OK (different make to usual) and there was one other unusual fault.

Wiring can be a mix of woven impregnated sleeving, PVC and Rubber in one 1950s radio. The Rubber can be all cracked and perished. But not always.

A regular multimeter is no good to test old capacitors used for more than 20V even if it has a capacitor range. You need to test leakage at 100V to 300V. A capacitor measuring "open circuit" (more than 2M Ohms on cheap DMM or 20M Ohms on an expensive meter) can be less than 0.1M Ohms when there is more than 100V across it!

Also it's easy to introduce faults by miswiring changing too many parts at once. Some parts have very different modern alternatives, or need two parts to replace them or have to be remade.
Faulty coil
http://www.radiomuseum.org/r/ever_sky_casket.html

Or someone may have "tightened up" all the little brass screws or dust iron cores and a signal generator is needed to re-align it.

What model is it (include a small photo 3/4 view front and straight view looking to inside at back) and I maybe can tell you who might be able to fix it?
Really whatever is charged will likely be a favour by someone that loves fixing old sets. A commercial rate isn't viable.

The meter sounds like an Electrician's model, not for Electronics. One for Electronics needs 2mV lowest range and safe to use at over 500V DC. Current needs to be from 1mA full scale to maybe 200mA with maybe a separate 10A max socket. It wants to to have 10MOhm input impedance on voltage and measure up to 20M Ohms.

The cheap meters in Maplin/Lidl/Aldi are only good for very basic low voltage and car electrics as they only are 1M Ohm input impedance and while they have 750V DC range, they usually are unsafe above 200V DC and die with a flash at 500V. The AC volts is barely safe to measure home mains and unsafe / unsuitable for Mains Radio/Amplifier secondary AC HT or 3 phase mains.

fraglerocks

Watty, yer depressing me more with each reply you send me! Attached are a few photos of it. It's definitely a Murphy A168.

watty

fraglerocks wrote: »

Watty, yer depressing me more with each reply you send me! Attached are a few photos of it. It's definitely a Murphy A168.

Yes, would require some thought but not a hard set to restore. Don't be tempted to sand the cabinet!

Simply clean alternately with soapy water and white spirit with a final wipe of meths. Use "furniture" scratch pens or markers on any scratches. If desired a couple of light coats of Acrylic spray lacquer/varnish (Not polyurethane!). Car transparent "top coat" is same stuff, but you may get the Acrylic spray cheaper in a hobby shop than Halfords (€7.50 vs €14)

You need a more suitable multimeter and some way of testing capacitor leakage. Using 20 x "euro shop" PP3s plugged in series (about 200V!) and put an electronics DMM in series in with capacitor, 100mA fuse and meter in current. The leakage needs to be under 1uA, So the Meter needs a 20uA range, or at worst a 200uA range.

Or unplug all valves (except the rectifier) and disconnect a suspect capacitor at one end and put meter on uA range in the break and power up.

I made a capacitor tester from the flash part of €4 "one use" Kodak camera.

If you are passing Limerick any time you could call by