HMV's not my usual brand of radio, I stick to AWA's but I've been given a couple of reasonably complete HMV's, a 61-51 and what I think is a B13C that I'm going to restore for my daughter who loves all things retro.

Being common radios I though schematics would be easy to find. Unfortunately the usual searches have turned up nothing apart from the miniature on Radio Museum.

Would anyone have the circuit and info for theses radios they could email to me?

Warren

PS I've just discovered there are two versions of the B13C, 6AQ5 and 6M5 output valves. The valves have been removed so I don't know which output valve it should have. The circuits would tell me.

There is an easier way with the outputs of B13C.

Set is listed in AORSM's: 6M5 which is getting hard to get, can be substituted with a small mod; has 9 pins; 6AQ5 7pins.

61-51 is also in AORSM's

Have both circuits.

6M5 can be replaced with the video OP valve 6CK6

BUT...... The suppressor in 6M5 is internally connected and with 6CK6 is external viz. pin 6

To not destroy the 6CK6 Pin 6 is wired to pin 3 Cathode making sure that if pin 6 is used as a tag of convenieince, whatever is on it is, removed.

Marc

Thanks Marc, it's all 7 pin so 6AQ5 it is!

Surprisingly in my box of valves I actually do have a couple of 6M5's but no 6AQ5's. I do have a couple of 6AQ5's in an old stereo amplifier I tinker with every now and then but I'm loathe to separate them.

Not really a problem at the moment, I'm just gathering what I need for these two HMV's - schematics, caps, valves etc. The actual resto's are a bit further down the track.

Cheers,

Warren

I just found this guide for substituting hard to get 6M5's with 6BQ5/EL84's. The good news about the 6BQ5/EL84 is that it is in current production.

Do fit earthed cables to those. The circuit shows shielded transformers and those bleed a charge to chassis, which is best removed.

I have measured 185V on some sets. It is a static charge and not indicative of a defective transformer.

Marc

Thanks to Graham who sent me the circuit for the 61-51 but I'm still hoping for one for the 6AQ5 B13C...

Cheers,

Warren

Warren,

I've just emailed to you the B13C circuit.

Cheers.

Thank you for the information Monochrome625!

Those pages are incredibly comprehensive, what publication are they from?

I'm storing away all the info on valve substitutions, I'm sure the sad day will come when this is the way (working) restorations are done. I haven't needed to replace too many valves, and the few I have I was lucky enough to find replacements easily.

Do fit earthed cables to those. The circuit shows shielded transformers and those bleed a charge to chassis, which is best removed

Marc, does this apply to both these HMV's? Is the core being earthed the shielding? That reminds me of when I did my training many years ago. A lot of the training material was from the good old US and we were warned that their neutral, at the time, wasn't tied to earth as ours is and it could potentially float at 100's of volts above earth on 120v mains. That would induce more than a static shock. I don't know if this is still the case over there.

Cheers,

Warren

The HMV B13C circuit is from the AORSM (Australian Official Radio Service Manual) volume 11, 1953 for 1952 radios. Unfortunately I don't have the HMV published service manual for this set as there would likely be a few more pages in it than the AORSM version.

I've heard the AORSM's mentioned a few times now. I saw an add somewhere for a full set of PDF's on CD for about $100, which I thought was a lot of money. I understand that original volumes go for big $'s so maybe $100 not so bad after all. I'll have to convince the treasurer that they are an essential tool (and useful in the kitchen too!)

$100 is not bad considering the time and effort going in to scanning 14 volumes at an average of 400 pages each. Most of my AORSM books ( I'm missing volumes 3, 4, 9 & 14) are all falling apart. I get the impression these books were not that well made to begin with. Makes it easier to scan though.

Cheers.

Earthed cable applies to both. If you look at the transformer drawing on the circuit diagram you will note the earth symbol eminating from the core.

That is the convention for a shielded transformer. This also causes confusion when testing them, as there is always a single open circuit, wire left over with no obvious owner.

You may have to relocate the wire as with sets like the 52-62 as the cable may crack the cabinet. I did manage to spot a roll of 3core flex that is only 6mm dia at a wholesaler. Even that is risky.

Tying knots in the cable is no longer legal. I normally use a gland if the set has not got a decent clamp. These can be mounted with the pointy end in and actually stop the cable rotating, which is one way they can flex fail.

I am actually a moderator for an American site . Some of their doings are scary & we have built some sets just as deadly here.

One must be careful; There are many American & European sets that have no transformer. We actually made a few to accomodate the fact that we did have towns with DC mains.

It always pays to look at the set carefully to see what it is and establish what condition it is in: Many are just not in a safe state to plug in without work.

Marc