Grant PC-409AC (made 1980) help please

[dt307]

945 m8 dont even think of 458's just bin them 2sc711 also will work fine but must be turned 180 deg and opp to the screen print , if you cant find any pm me and i send you a hand full

[cb4ever104]

IF I SEE ANY 2SC458 in an older uniden chassis i remove them instantly <<DO THIS FIRST
they are by far bar none the biggest problem to hit the 8719 type chassis

I really need to start writing all these tips down somewhere ....

[dt307]

i dont see them on the schematics only the 1 next the audio chip and it seamed to be only the early production runs i guess they ran out and had a boat load of 458's in stock and subed them, like i said its common on stalkers madi's washingtons ect to hear a hissing noise ,its not much but know its there .when the volume turned off or when you got the radio in rx and the squelch up or static crackle sounds in rx swap out that 458 and she is all good

[GT390]

Great advice, thank-you again, I had already ordered some 945`s they should be here soon, I am back on 12hr shifts until next weekend so may not get at it again until then. Brilliant idea with the smart phone , I do have a AF genny but it is very old and puts out a very weak signal, connecting it to the mic audio input attenuates the signal to almost nothing but inputting the signal from the smart phone through the mic I was able to pick up the sine wave on the scope almost everywhere on the board...even probing from ground to ground on the chassis ??? I have another grant the same opened up on the bench to compare and it does not produce the same results...seems like I am sending audio to ground somewhere??

[GT390]

well, the new 2SC945`s arrived today and I replaced TR23 which was a 458, initally I thought the problem had gone as keying the mic I got no his crackle and noise on the receiving set, then I realized that was because I had lost most of the gain, I had to turn the mic gain up full to get any audio transmission out. I had ordered some new 458`s at the same time so tried one of these and all the gain came back, along with the audio problem so I guess the 458`s must have a lot more gain than the 945`s, hopefully I will get the other 945`s in that path swapped out tomorrow night to see what happens..

[GT390]

OK, so it seems the 945`s I bought don`t work in this circuit.. I replaced TR21 and TR22 with the new ones I bought on flea bay and keying the mic all I get on receiver is a solid tone with no audio whatsoever, I put the old 945`s back in and audio returns, they are marked 2SC945 Y, the "Y" on the data sheet refers to Hfe 120 - 140. ECB pin out is the same as any 945 datasheets I can find. They are NPN, should I have used PNP ?? I have sent you a PM chris

[GT390]

Dam.. the pin out on the flea bay ones are EBC instead of ECB...

[cb4ever104]

Dam.. the pin out on the flea bay ones are EBC instead of ECB...

Don't thing they're original then . The 945 has always been BCE .

http://www.unisonic.com.tw/datasheet/2SC945.pdf

Sammy

[163TM847]

What seller did you get the 945s from ? I ask as there is a certain seller who i have bought from several times and they have always been fake, Also as a side note 2SC710 is a 2SC945 equivalent, 2SC711 is a 2SC1675 equivalent

[GT390]

Yes I have now realised all the modern versions of the 2sc945 have EBC pin out, I found an article on it on a HiFi website explaining this,it says the proper early japanese made 2SC945 were BCE but all later chinese versions are EBC, farnell and RS say the KSC945 is a replacement, it also has the incorrect EBC pins. I crossed the pins over and heatshrinked them and they still produced no gain in the circuit, I guess they are re-branded china rubbish. I finally managed to find some C945 with the BCE pin out and have them on the way to me, and then found a place in Hong Kong who claimed to have genuine n.o.s. nec 2SC945AQ which is the exact spec used originally. I ordered some but not too hopeful of them being what they say they are..we shall see when they arrive

[GT390]

The flea Bay ones were bought from langrex, a seller I have used many times before usually for valves and never had any problems before

https://rover.ebay.com/rover/0/0/0?mpre ... 0844041870

[dt307]

sorry been mental here with new grandson some 711 in the post bro

[cb4ever104]

sorry been mental here with new grandson some 711 in the post bro

Shouldn't they be 710's ?

[GT390]

I got some 945`s with the correct pin out and 733`s and replaced all TR21 to TR27 and saw some improvement and much less "white noise" on transmit but audio was still low and slightly distorted, I replaced the 458 (TR43) beside the audio chip with a 945 and swapped out C46 from a parts rig (links TR43 to TR21), swapping C46 made an improvement on the audio level to a receiver but it is still slightly distorted, I aligned the PLL section and TX this made another slight improvement but receive now is off frequency a bit ?? I will align that once I get my AF genny sorted.
So I still have the problem albeit much better than it was, I think I will replace the other green caps in the audio path as changing C46 did make a fair difference, what type of caps are they ? green dipped rectangle shaped are they poly, ceramic or tants ?

[dt307]

sorry been mental here with new grandson some 711 in the post bro

Shouldn't they be 710's ?

yes m8 your correct
2SC710 is a 2SC945 equivalent, 2SC711 is a 2SC1675 equivalent but uniden fitted 2sc711 in backwards in many radios that are marked 2sc945 in the schematic from new......so if its good enough for them lol