Okay... I really don't like saying this, but have you got a BC109 handy that you could put in place of one of the BC186s?
It's this lack of collector volts that's bothering me.
That I do!
will give it a go tomorrow. Fed up now….. haha. Is this an acceptable replacement or more of a “test and see what’s what”?
Bit of both, really; for now, it's a "try it and see" measure. As you've probably determined, I'm not a great fan of what I understand our American cousins call "The Parts Cannon", whereby you just keep throwing parts at something in the hope it'll eventually come good but it's difficult to come up with an effective diagnosis remotely.
You can get BC186s from Langrex, but either a BC109 or a BC549 would do as a replacement in this position.
Okay... I really don't like saying this, but have you got a BC109 handy that you could put in place of one of the BC186s?
It's this lack of collector volts that's bothering me.
That I do!
will give it a go tomorrow. Fed up now….. haha. Is this an acceptable replacement or more of a “test and see what’s what”?
Bit of both, really; for now, it's a "try it and see" measure. As you've probably determined, I'm not a great fan of what I understand our American cousins call "The Parts Cannon", whereby you just keep throwing parts at something in the hope it'll eventually come good but it's difficult to come up with an effective diagnosis remotely.
You can get BC186s from Langrex, but either a BC109 or a BC549 would do as a replacement in this position.
The board is looking more and more like i've done exactly that anyway..... what a nightmare. Remind me never to touch one of these again!
OK. With a BC109C (all I had) I get two lots of 10.49V DC and 2.3V ish so I guess that identifies the transistor is at fault? I seem to have both channels now too
OK. With a BC109C (all I had) I get two lots of 10.49V DC and 2.3V ish so I guess that identifies the transistor is at fault? I seem to have both channels now too
OK. With a BC109C (all I had) I get two lots of 10.49V DC and 2.3V ish so I guess that identifies the transistor is at fault? I seem to have both channels now too
OK. With a BC109C (all I had) I get two lots of 10.49V DC and 2.3V ish so I guess that identifies the transistor is at fault? I seem to have both channels now too
Where were you measuring those voltages, Jamie?
Base of RH VT1 when replaced with a BC109c
So, let's be clear (because this is important): was 10.5V on the collector and 2.3V on the base?
Also - has it made any difference to the sound level?
@cathovisor correct as for sound not checked just checked voltages not a lot of time this afternoon but seems to be outputting now both channels from mains him it has
@cathovisor correct as for sound not checked just checked voltages not a lot of time this afternoon but seems to be outputting now both channels from mains him it has
Ok. Idiocy avoided. What I did was I didn’t realise the BC 109 and BC 186 had the emitter and collector the wrong way round…. Doh. Corrected, and we now have one full output channel which sounds crystal clear! So…. RH is sorted.
LH channel is struggling, it’s output remains lower and distorted. Noting the lower voltage output a few posts up, I changed this for a BC109 too. Which still produces distorted sound although at a higher volume. Voltage is still lower on this channel than on the (now healthy) right channel!
So I assume there must be something amiss in the supply on the left channel, that is already changed in the right channel. No doubt this failure is what causes the original transistors to fry themselves!
Ok. Idiocy avoided. What I did was I didn’t realise the BC 109 and BC 186 had the emitter and collector the wrong way round
Erm, I'm confused as to why, data states the pin outs are the same. To be doubly sure, I've confirmed by physically testing a BC109 and BC186. However, it is interesting with your developments.
Ok. Idiocy avoided. What I did was I didn’t realise the BC 109 and BC 186 had the emitter and collector the wrong way round
Erm, I'm confused as to why, data states the pin outs are the same. To be doubly sure, I've confirmed by physically testing a BC109 and BC186. However, it is interesting with your developments.
Just another observation but a BC109 is NPN whereas a BC186 or BC153 is PNP.
Good Lord, I must have been slipstreaming when I suggested a BC109 - well spotted! I'd forgotten the chassis was "positive earth" and so looked at the voltages as though they were for an NPN device.
So to be correct, it should be either a BC179 (metal body) or a BC 559 (plastic body).
Just another observation but a BC109 is NPN whereas a BC186 or BC153 is PNP.
Good Lord, I must have been slipstreaming when I suggested a BC109 - well spotted! I'd forgotten the chassis was "positive earth" and so looked at the voltages as though they were for an NPN device.
So to be correct, it should be either a BC179 (metal body) or a BC 559 (plastic body).
Mea culpa, mea maxima culpa...
I mean one side works 😂😂 left. One doesn’t do well…… hmmm so it’s a no go then! I’ve ordered some BC153s
So... call me stupid, but how come the channel is bursting with life and sounds good with an incorrectly polarised transistor in situ? Does this still point to a fault within the circuit... or do they work in reverse (but not for long)
The BRC/Thorn publication - A Guide To Semiconductor Replacements May 1971, lists three approved alternatives for class AF13 medium gain PNP.
Two of those have already been mentioned (BC153 and BC186) both of which were never widely used. However BC213L is also listed which has a lowish hFE starting at around 40 but typically 80 upwards. These often appeared in BRC radio and TV products.
A quick simulation of this circuit with a BC212 shows collector voltage settles at just under -8V, emitter -1.62V and base -2.26V, assuming measurement is taken with respect to the positive ground/earth. Also a measurement tolerance error is to be expected as these were originally taken using an AVO 8 or equivalent meter with 20kΩ/V sensitivity.
