Roberts R600 LP1171 module

[tracypaper]

Hi All.
Been looking at threads and youtube vids on how to fix these radios and have got to the stage where I have had to take the push buttons out as they are fixed to a board and completely in the way of the LP1171, which is also now removed and opened up.
As per info contained in threads the module has two AF116s and a AF115.
Questions are
Do I still have to replace the AF11s with AF125 or AF127 or combo of both? or is there something better now?
4 of the 5 electrolytics have a black band around one end is that the negative end? the other has a ridge in it, is the ridge the negative end? they are quite small and don't state polarity as the bigger ones do.
Cheers.
Gaz.

['LIVEWIRE?']

You could also use Russian Germanium transistors, usually available on eBay for around £1 each (in packs of 5 or 10, IIRC). The leads on these are ca.25mm long, making them easier to fit than the AF11x types, besides which they are considerably cheaper!

[tracypaper]

Sorted the caps just looked on google for polarity.
Is there a part number or name for the Russian transistors so I can look them up.
Gaz.

[martin.m]

Just search on Ebay for "russian germanium transistors". Even if you have to pay for overseas postage they are still good value.

[tracypaper]

Found the part number on another thread GT322.
Cheers

[nebogipfel]

GT322b seem to have the best gain

['LIVEWIRE?']

IIRC, the pin-outs of the GT322 series are the same as the AF11x series, but they (usually)come with a data sheet showing connections.

[poppydog]

Be aware that when replacing af11 types with gt322b transistors, the leadout orientation is very different, meaning that the Russian leads end up being very contorted. This means that they cross over each other so sleeving is essential, couple that to the fact that the leads will have to be kept very short for the module cover to go back on meaning patience is required, I have done about 5 modules now with gt322bs with great success, see my thread here has pics etc.

https://www.vintage-radio.net/forum/...d.php?t=143394

I have never been able to get any gt322bs with 25mm long leads.
regards poppydog

[tracypaper]

Due to the long wait in delivery times from Russia (end of Jan) I have gone for 3 AF127s instead.
I will google the pin outs but any help much appreciated.
Gaz.

[poppydog]

I could sort you out 3 gt322bs, if you change your mind PM me.
regards poppydog

[Radiocruncher]

Hi Gaz. AF127’s will be fine and would be the preferred substitute for the old transistors. The GT322B is a good substitute and it’s the cost that makes them worth considering as they are around a third of the cost of an AF12x type. The legs of the AF127 will still cross over. Get yourself a fine tipped marker pen. Take the old transistors out one at a time and mark the pinout on the board. It will save a lot of time and head scratching.

Good luck

Graham

[tracypaper]

Well got the GT322b transistors in and changed all the electrolytics in the LP1171 but the MW and LW is still dead as a DoDo, sound was louder on FM (ear phone jack wires disconnected and hot wired together) for some reason, but at a loss?
Gaz.

[GeoffK]

Might have been better to change one thing at a time, electrolytics are leaky even when new so don't need changing just because of a bit of leakage or slight lose of value. Make sure any replacements are the correct way round. Same goes for the transistors, were they good devices before fitting, have they been damaged by the fitting process/ A transistor can have a basic check in-situ with the diode range of a multimeter for forward/reverse junction working. Practice with a germanium diode to see the difference if you aren't sure. Voltage checks could be done, there should be around 7 or 8 Volts on each collector. If the positive lead goes to chassis then this will show a negative sign before the voltage. The emitters (for PNP transistors) are always taken to the positive rail, usually via an emitter resistor and have a lower voltage on the emitter, with a typically 0.2 or 0.3 voltage difference between the emitter and base of the transistor if the transistor is working correctly. The base emitter voltage of the oscillator transistor might only have 0.1 v difference, the emitter may even be slightly higher than the base. Other things to check are the wave change switch. Good luck with it.

[crackle]

Originally Posted by tracypaper

Hi All.
4 of the 5 electrolytics have a black band around one end is that the negative end? the other has a ridge in it, is the ridge the negative end? they are quite small and don't state polarity as the bigger ones do.
Cheers.
Gaz.

The aluminium end of an axial electrolytic is always the negative, the insulated end is the positive.

Mike

[tracypaper]

Trouble is the transistors in the LP1171 can not be voltage tested in situ. Will take it out again and diode test them, I never thought to test them before re-fitting the Module.
The switch bank has had nearly a full can of Servisol sprayed into it so don't think its that?
Gaz.