Grant PC-409AC (made 1980) help please

A forum for the discussion of matters of a technical nature. All such activities are undertaken at the readers discretion and own risk. If you don't know what you are doing, don't blame us if it all goes wrong!
User avatar
cb4ever104
Veteran
Veteran
Posts: 4958
Joined: 28 Jul 2011, 21:26
Location: Alicante , España

Re: Grant PC-409AC (made 1980) help please

Post by cb4ever104 » 09 Apr 2019, 10:47

dt307 wrote:
09 Apr 2019, 10:44
.....so if its good enough for them lol
:thumbup:
30TM060
Paul aka "Sammy". (108) PY60 Old Paisley DX Group (RIP Rab Markie)
Ex GM0 , now EA5 .
Handle "Fortune Hunter" back in "the day"
Radios ....? Anything that says "TAIWAN R.O.C" on the back.

User avatar
dt307
Top Poster
Top Poster
Posts: 1209
Joined: 05 Sep 2014, 16:15
Call Sign: 163dt307

Re: Grant PC-409AC (made 1980) help please

Post by dt307 » 09 Apr 2019, 10:49

GT390 wrote:
08 Apr 2019, 20:51
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 ?
the green caps Polyester Capacitor polly film
163dt307-chris




“I fear the day that technology will surpass our human interaction. The world will have a generation of idiots.”
― Albert Einstein

User avatar
Otter
Veteran
Veteran
Posts: 2794
Joined: 04 Apr 2008, 21:42
Call Sign: 26TM439

Re: Grant PC-409AC (made 1980) help please

Post by Otter » 09 Apr 2019, 20:30

GT390 wrote:
08 Apr 2019, 20:51
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 ?
They're polypropylene caps, but I have never heard of one going wrong. Ever. Since 1980. Not a single one.
"To this day the words Stirling bridge conjour pride in every Scotsman's heart, while to an Englishman those same words conjour literally no feelings at all." - Cunk on Britain S1 E1
Gorgon Brown - a man with all the joie de vivre of a haunted cave in Poland. S1 E3

GT390
Regular
Regular
Posts: 39
Joined: 10 Jan 2018, 00:23
Call Sign: 68TM027

Re: Grant PC-409AC (made 1980) help please

Post by GT390 » 10 Apr 2019, 13:03

Otter wrote:
09 Apr 2019, 20:30
GT390 wrote:
08 Apr 2019, 20:51
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 ?
They're polypropylene caps, but I have never heard of one going wrong. Ever. Since 1980. Not a single one.
I thought too that they were pretty bulletproof and the one I replaced c46 tests OK as far as I can test it. It's got me wondering now why it made a fair difference changing it. I have ordered up some new poly films anyway.

GT390
Regular
Regular
Posts: 39
Joined: 10 Jan 2018, 00:23
Call Sign: 68TM027

Re: Grant PC-409AC (made 1980) help please

Post by GT390 » 27 Apr 2019, 16:48

dt307 wrote:
06 Apr 2019, 11:12
sorry been mental here with new grandson some 711 in the post bro
Chris can you PM your paypal email and I will send you a thank-you

Thank-you to all who helped get to the bottom of this, the fault was electrolytic C191 right at the band selector switch....installed wrong polarity..duh

Image
All working fine now, thinking back I must have only made contacts on FM after installing the new caps and FM is on a separate board on this early set

thanks again
Robert

Post Reply