Hi friends, i have a strange problem with a PC-999AB Grant. Sometimes the ref osci 10.240 stops working. Swaped all electrolytic caps, swaped C108/109, swaped the xtal.
If i do some tests with the PLL at pin 8, the osci starts working again for some time. VCO voltage is ok, but drops down to 2,0v when osci stops working.
Any ideas? PLL chip?
73, Ralf
President Grant PLL/VCO/10.240 oscillator Problem
- 13EL121
- Radio Addict
- Posts: 618
- Joined: 16 Sep 2008, 20:55
- Call Sign: 13DA121
- Location: Germany
- Contact:
- cb4ever104
- Legend
- Posts: 6562
- Joined: 28 Jul 2011, 21:26
- Location: España
Re: President Grant PLL/VCO/10.240 oscillator Problem
Hi Ralf .
Yeah . I'd try swapping out the 8719 PLL and see what happens .
Sammy
Yeah . I'd try swapping out the 8719 PLL and see what happens .
Sammy
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.
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.
- 13EL121
- Radio Addict
- Posts: 618
- Joined: 16 Sep 2008, 20:55
- Call Sign: 13DA121
- Location: Germany
- Contact:
Re: President Grant PLL/VCO/10.240 oscillator Problem
Yes Sammy, hope that it is the PLL. Hope tomorrow the replacement will arrive. A friend of mine has two MB8719 in stock. The voltage is to low at Pin7/8. Pin6 is low, so VCO is not locked. Nearly all voltages at the PLL are to low...compared to my working Grant. But.Vdd is ok at Pin9 with 8v. Sometimes the 10.240 osci starts working, Then voltage at Pin7/8 is round about 2,8v. But suddenly it drops down to 2,4v and osci is not working.
Will see...
Will see...
Last edited by 13EL121 on 10 Sep 2018, 21:00, edited 2 times in total.
- 13EL121
- Radio Addict
- Posts: 618
- Joined: 16 Sep 2008, 20:55
- Call Sign: 13DA121
- Location: Germany
- Contact:
Re: President Grant PLL/VCO/10.240 oscillator Problem
The binary adders are ok for shure. Maybe a shorted cap has killed the PLL. There were some grey YEC 10v caps that were shorted. The 100uf in the VCO area was one of them.
- KlondikeMike
- Super Member
- Posts: 107
- Joined: 06 Jan 2014, 03:59
- Call Sign: 9WR2000
- Location: Edmonton, Alberta, Canada
- Contact:
Re: President Grant PLL/VCO/10.240 oscillator Problem
Yikes! Most likely. There are many of those YEC 10v caps in the HR2510 as well.
- 13EL121
- Radio Addict
- Posts: 618
- Joined: 16 Sep 2008, 20:55
- Call Sign: 13DA121
- Location: Germany
- Contact:
Re: President Grant PLL/VCO/10.240 oscillator Problem
Indeed. The grey YEC 10v ones are a main Problem of 20-30 years old Uniden radios. The blue caps from Rubycon are not affected. But the grey ones have to leave all my radios.
- 13EL121
- Radio Addict
- Posts: 618
- Joined: 16 Sep 2008, 20:55
- Call Sign: 13DA121
- Location: Germany
- Contact:
Re: President Grant PLL/VCO/10.240 oscillator Problem
Update: PLL swaped. Radio seems to work fine now. All voltages at the PLL pins are now in specifications. Maybe a shorted cap has blown the PLL.
- cb4ever104
- Legend
- Posts: 6562
- Joined: 28 Jul 2011, 21:26
- Location: España
Re: President Grant PLL/VCO/10.240 oscillator Problem
Could be Ralf . I've had a few Presidents with shorted caps around that area . Glad you got it sorted .
Sammy
Sammy
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.
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.
- 13EL121
- Radio Addict
- Posts: 618
- Joined: 16 Sep 2008, 20:55
- Call Sign: 13DA121
- Location: Germany
- Contact:
Re: President Grant PLL/VCO/10.240 oscillator Problem
Radio works great now. No faults anymore. Did a full recap as there were the grey YEC caps inside. The new chinese 105 degrees JWCO and KY caps will do the job for the next one or two decades...
These caps are also in the new President radios. So they are not too bad for the money i think.
These caps are also in the new President radios. So they are not too bad for the money i think.