Grant PC999AC rx issue AM/FM

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ch25
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Re: Grant PC999AC rx issue AM/FM

Post by ch25 »

So IMO problem is before that filter. FL2 or (and) TR8
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Re: Grant PC999AC rx issue AM/FM

Post by tcom75 »

FL2 has 3 pins. One pin goes to L13, center pin to ground and the other goes to R86.
I suppose you want me to jumper with a capacitor between L13 and R86, right?
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Re: Grant PC999AC rx issue AM/FM

Post by ch25 »

Exactly
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Re: Grant PC999AC rx issue AM/FM

Post by tcom75 »

Jumper done with a ceramic capacitor (code is 150K NPO) .. that's what I have here at the moment.. nothing has changed.. not sure if value of this cap is enough or perhaps too big..
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Re: Grant PC999AC rx issue AM/FM

Post by tcom75 »

To be precise with or without FL2 installed I cannot hear any difference and by adding the jumper cap is still the same
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Re: Grant PC999AC rx issue AM/FM

Post by ch25 »

I could help you more in a few days, I have PC999 Grant I could do some measurements to verify, but a few next days are busy for me :)
Chris
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Re: Grant PC999AC rx issue AM/FM

Post by tcom75 »

Tks Chris, take your time! Merry Christmas.
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Re: Grant PC999AC rx issue AM/FM

Post by dt307 »

sorry i am afk maor death in family today so no fit state to wire a mic to a gecol let alone help any1
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Re: Grant PC999AC rx issue AM/FM

Post by cb4ever104 »

dt307 wrote: 24 Dec 2018, 00:16 sorry i am afk maor death in family today so no fit state to wire a mic to a gecol let alone help any1
Sorry to hear that Chris . Hope things aren't too bad .

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Re: Grant PC999AC rx issue AM/FM

Post by tcom75 »

Hi everyone, HNY !!!
Back from holidays..issue with Grant not yet fixed. I removed FL2 and made a jumper as suggested but I did not see any effect at all.

Can someone drive on next step in order to better define where the problem could be before I start replacing caps? I'd like to get close to the area where a component could be on failure..

Thank you.
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Re: Grant PC999AC rx issue AM/FM

Post by tcom75 »

Back on this issue as I didn't have time until now.
So I removed FL2 and made a jumper, however I did not see any difference.

Assuming the next step is to check TR8, is there a way to test it without taking that out from the board? If not what would be the measurement to be done with the transistor off the circuit?
Thank you.
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Re: Grant PC999AC rx issue AM/FM

Post by matt_ne »

tcom75 wrote: 22 Dec 2018, 20:18 Hi everyone,
I just found a new old stock CB President Grant with PC999AC board. The radio has been sleeping for more than 3 decades till few days ago when I found a dealer with this new radio (box never opened).
Does the dealer have any more of these? I'd quite like one!
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Re: Grant PC999AC rx issue AM/FM

Post by dt307 »

ok back lol

i suggest you send to nick or some 1 for repair m8 but if you want to do it your self please follow whats been said

look and read what i told you about checking voltages and doing an alignment this alone will point you in the area as a bad cap/ic/transistor

what i have seen many many times is glue under fl1 gone bad under the am/fm 455 filter shorting it out

remove fl1 clean any glue and before you refit hold a high value disc cap on the input and output this will tell you if the filter dead

as for checking a transistor in circuit if its gone short you would have seen this already in the voltage checks

and an "open " transistor can be checked easy with a high value cap marked 103 104 ect held on the solder side of the transistor on its input and output (this how i used to do it...now i just pull them and put in a transistor checker)

inc is the sig path yellow all modes blue and purple fm / am
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Re: Grant PC999AC rx issue AM/FM

Post by matt_ne »

Five minute job with a signal generator and a scope.
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dt307
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Re: Grant PC999AC rx issue AM/FM

Post by dt307 »

matt_ne wrote: 11 Mar 2019, 22:50 Five minute job with a signal generator and a scope.
i know and true but most people wont have that equitment so only way to help is to go back to basics
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