Help this newbie fix this Cleartone T7

[hotshot6120]

Im trying to advance my skills in radio repair and learning the hobby. I can test, service, troubleshoot and solder just fine, but my radio skills are new, and I am learning daily.

I really want to help a friend fix his Radiogram. Its a mid 1960s Canadian Cleartone. The Radio part is a T7 transistor.

the Schematic was supplied index the unit.

I put a bit of Contact cleaner on the pots, cleaned the surfaces with 99% ISO. Will polish the RCA inputs shiny again.

Heres what we have deduced:

We hooked up an iPod to the Tape AUX in. The only issue was us trying to figure out what the Reverse button does. we think its a channel swapper but as to why it's there I don't know.

Nothing crackles and sounds good. I used this method to isolate if its a "radio" issue or a system issue.


Now the Radio:

Issue 1

When you adjust the balance, you get odd results.
-Full left goes quite to off.
-Full Right appears to work fine.

when you hit reverse the opposite happens.

If i push and pull on the Balance Pot, you get cracking, popping and intermittence. Yet in the AUX setting the Pot is fine?

Issue 2

She hums a little

There are a ton of these English Plessey Electrolytic Caps. They all look as if time has beat them up a bit.

I have heard some say, replace all electrolytics. I have hear others say, you only have to replace the ones that are broken, and I've had others say, that only the Tone Circuit is where you want to be carfull to match the Caps to stock as that's what changes the sound?

Am I missing something and can I advance this with my Multimeter, or am I at the stage to hand it over to a Pro tech, thus not learning anything?

I feel as if i just need to be pointed down a path..

Appreciate all help, so far you guys have been a wealth of knowledge


Cheers,

[Edward Huggins]

Those Plessey Red'n'Yellows are not good news I'm afraid. By now most of these will be suspect and my goodness you have a few! Edward

[Station X]

It looks like it'll be easy enough to change them though.

[Tom_I]

The "reverse" key on these radiograms swaps the stereo channels over.

The idea is that if you are sitting with your back to the unit, you throw the reverse switch so that the left and right information is still in the correct orientation.

[julie_m]

Now that's cunning!

[Herald1360]

But if you sit with your back to the orchestra/band nobody would swap them round for you.......

[dave walsh]

That probaly seemed like a good idea/gimmick at the time, when Stereo was so new but it assumed the listener would even notice and be prepared to jump up and throw the switch In the North, my sound system is forward ie the fireside alcoves and in the South from the rear. I can't say this bothers me at all but then I'm listening to the music not the Stereo Field. In the Radiogram days, [should you be able to afford one]. it was often not possible to position the RG in front anyway, as the seating emphasis was on the fireplace but nobody was bothered.

Dave W

[hotshot6120]

Awesome, thx!

[hotshot6120]

Originally Posted by Edward Huggins

Those Plessey Red'n'Yellows are not good news I'm afraid. By now most of these will be suspect and my goodness you have a few! Edward

So, would it be acceptable to just cut the Red n Yellows out and put in new ons of the same values? If so, what kind does one recommend. It would just be a Swap job correct?

[Edward Huggins]

Basically yes. Of course some of these may still be OK, but we don't know which. You will need to have the same voltage rating and as close as possible to the capacitance values.

Edward

[Station X]

I think the use of turret strips should make it easy enough to unsolder the caps rather than cut them out.

['LIVEWIRE?']

At the risk of repeating readily available information, may I point out that modern capacitors (and, for that matter, resistors) come in 'preferred values' of 1, 2.2, 3.3, 4.7, 6.8, 8.2 and their multiples, so, e.g., a 50uf capacitor's equivalent is a 47uf, whilst a 32uf would be replaced with a 33uf. Since electrolytics have a wide tolerance over their nominal values, this isn't importtant. In addition axial leaded capacitors, i.e., those with one lead at each end, are available, although radial leaded types are more common. The latter can be used as replacements for old axial types. I have often used them myself . As to stereo amplifiers, etc., with a 'reverse' switch, I once had such an amp., but cannot recall the make or model. Bit of a gimmick, IMHO!

[hotshot6120]

Fantastic info. Thank you. It's all new to me. So if I understand the points made,

1. I can use a ( what I call Can type Cap with vertical leads ) to replace the axial Plessey's

2. Same Voltage is critic but capacitance can vary over slightly.

I know there's a POS / Neg to caps, but it's there better kind of brand? Something I should be looking for, say a UK or US made vs China.. For tone?

Also, what's the best way to test a Cap. My multimeter does Capacitance.

Thanks again folks.

[G8HQP Dave]

Same voltage is not critical; sufficiently high voltage may be critical. If the original is 16V then you can replace with 16V, 25V etc. but probably not 10V.

Don't worry about brands, provided you buy from a proper component distributor. If you buy cheap Chinese caps off ebay then they may be fine or they may be completely useless.

[hotshot6120]

Perfect. I won't buy crap. I'll go to a local shop. So higher on V and Uf. Excellent.

[Goldie99]

Originally Posted by hotshot6120

[I won't buy crap. I'll go to a local shop

Not sure about shipping costs for Canada, but you'll probably find a wider selection, and quite possibly lower prices, with one of the major US based suppliers - e.g., Mouser, Digikey. Their online catalogues are also excellent, with good search capabilities.

Any chance you could post the schematic ? or point me to a copy if it's available online ?

[hotshot6120]

YES! Im taping in it up and have to scan it. tonight.

[hotshot6120]

Here are the originals. Too big to Scan, and they were ripped up so I had to tape them together..

In the fine print, it states what caps are mica, paper, and wax

['LIVEWIRE?']

AS a footnote to the above, I, and, AFAIK, most forum members regard waxed paper ('waxies') capacitors as 'replace on sight', especially in valved (tubed) equipment, though it's not always neccesary to change them in solid state radios.

[Station X]

I can't see any evidence of waxies in the pictures in post #1..