Bush TR82C

[Bushbaby]

Hi All,
I've started work on the recent TR82C acquisition from the recent Golborne swapmeet.

Its working of sorts and very crackly.

I've taken the chassis from the case, I removed the dial glass using dial cord behind it and gentle prised it away. I'm a wee bit concerned as I also tweaked the brass screw to the air cap thinking that it might go right through - have I created a new problem here??

Before I go further it suffers badly from the usual bent carry handle - how can I safely take of the handle from the body to rebend it WITHOUT cracking the case.

Any other tips would be most gratefully received.

Thanks

Rob

[Joe]

Rob, DAC90s may have asbestos in but these blinking things have got germainium!

I've only done one and didn't have to take the handle off so I don't know about that.

Hope you'll be feeling better soon.

- Joe

[Yorkie]

If it works, but just crackles, that will probably be the nasty push-button wavechange switch contacts.

If it has Mullard OCxx transistors it's a MK1, if it has AFxxx transistors it's a MK2. (The Blue/Chrome one is the TR82C - the Tan/Chrome one is the TR82D).

If it isn't tuning any stations, using your signal injector/tracer, inject a signal at the slider of the volume control. If you get a tone from the speaker, the audio stage is OK. Then using the RF probe, connect the signal tracer to the collector of TR3, which goes to the primary of IFT3. Swing the tuning cap across each band, and if you get tunable signals, all is well up to the primary of IFT3. Now transfer the probe to the top end of the volume control to see if you get signals there. If not, lurking inside the can of IFT3 is the detector diode - a known culprit on TR82Cs. If it's duff, replace it with any germanium diode such as OA90, 1N34 etc - it's not fussy, but don't use a silicon diode such as 1N4148, 1N914 etc.

If it's a MK2 with AFxxx transistors, you'll no doubt know about 'whiskers' and cutting the screen leads (make sure you cut the correct lead!).

Can't comment on your handle issues and I don't understand what you mean about the tuning cap screw. (IIRC, the cap is held on by three screws and rubber grommet jobbies). If there's a screw in the centre of the cap spindle, that's just there to space the 'push-on/won't-come-off' clear plastic knob (sometimes mistakenly called the 'dial') so that it doesn't rub on the case front as it rotates.

Bush data sheets are very comprehensive, and the one on the TR82C is no exception - it runs to 8 pages. Never use the manky 2-page Trader Sheets where Bush are conncerned. I can never understand why people who dabble about with DAC90As use the nafola 2-page Trader Sheet 1161 in preference to the 8-page Bush data sheet. DAC90As? Don't get me started!

Best of luck with it Rob.

[Bushbaby]

Thanks David,
The screw that I mention is the one that holds air cap (blades - I'm sure thats not what they are called) on the inside of the radio. I'm appears to be fine thread too.
It tunes in well on MW but receives virtually nothing on LW. It indicates its a 82C with a tan/cream case and AF117 although they are working. Its got Hunt small black caps and even though its working I am tempted to replace these.

Its cleaning up nicely - perhaps I should just leave the handle with a slightly lop sided appearance as it adds character!

Regards

Rob

[Mark R]

Rob,
Stick with valves lad, transistors are the work of evil!

I have no doubt you will fettle it. David is correct, check for the dreaded whiskers, Steve P has a good solution for them.

cheers Mark

[Steve_P]

Actually I have several ways.

The first one is to flick them quite hard. This can make the tin whiskers fall away and hey presto it works. For a time...

The second one is to cut the screen lead. Micacle cure! Until two pins of the actual transistor short out.

The third way is to heat them up with the iron. This is a newer technique that seems to work in some cases. Worth a shot.

The fourth way is to put a capacitor or a battery between Screen and the other three in turn. Blows the whiskers.

The fifth way is Replacement. AC127 etc will do here. Or you could go down the silicon route with the BF450. Although a silicon transistor, it will operate at a Germanium bias, although in some cases the set may need some realignment.

Actually, NASA are having trouble with these transistors too with some of their early stuff that's out there.

Cheers,

Steve P.

[tiv48]

with the af1xx give them a tap with a screw driver handle a faulty one should show up.
rob t

[Bushbaby]

If the set is working are they likely to fail?

[tiv48]

hi rob just a light tap not a hit
rob t

[Steve_P]

I've been knocked down for saying this, but I am fairly certain that there were good and bad batches of these transistors? They are either all OK or all bad in my experience. I have a Roberts R700 here with all the original transistors and it works great!

As for your question, they either work or they don't, so when they fail it's unlikely to be the cause of crackles. If they are OK, leave them. That's my philosophy, In a Bush TR82, check capacitors first, especially any with Hunts written on them or the Black + Red Electrolytics.

Cheers,

Steve P.