Advance P1 Sig gen - What HT Voltage? - UK Vintage Radio Repair and Restoration Discussion Forum

Ebrew567 · 30th Nov 2011, 3:32 am

Hi,
A previous owner has replaced the power transformer and PSU with a new concoction. I can have an HT voltage from 135 to 185 Volts DC (as measured at the second electrolytic smoothing condenser), by changing transformer taps (another story). The unit has had extensive replacement of old caps, electros and composition resistors (I'm still completing that).

What HT voltage should I aim for? Thanks

WME_bill · 30th Nov 2011, 8:12 pm

Advance P1. I have never seen a manual. Produced about the same time as the E2, which followed the Q1 and B4 models. All very much the same in performance. Must have been some marketing idea, or special models for the Military. But the usual oscillator valve for these models was 6J6 or 12AT7. Run them between 150 and 200V I suggest, the 135v may be a bit low. If you cannot get enough RF at max output, or it fails on the highest frequency, change the valve and/or increase the voltage. I suggest it is not very critical. Bill m0wpn

BobGreen · 2nd Dec 2011, 4:42 pm

The Advance E1 was like this - https://www.vintage-radio.net/forum/...6&d=1301076100

Ebrew567 · 9th Dec 2011, 3:30 am

Hi,
Thanks to the people who came back.
I increased the volts a bit to 140Vdc, I'm sure it should be higher, but its working fine on all bands and will be put to work as is (until I get around to it again).

Appreciated if WME Bill would send me a PM (Re his info on Avo AFM2)

Chaparal · 9th Dec 2011, 8:09 am

Here is the P1 signal gen manual.

It's in djvu format

Peter

amornummi · 27th Jun 2012, 10:01 pm

I have recently inherited a P-1 . Very clean , ex college.
Mains input 250 volts. Heater volts 7.2 . HT winding giving 57 volts. Measures 135 ohms.
Ht after silicon diode is 68 volts.
Audio out 20 volts peak. RF out at 3.5 megs is bit low at minus 10 Dbm.Works happily on all freq ranges to 100+ megs
Tempted to fit doubler to get a bit more output, an lose some lt to 6.3 v.

Station X · 13th Jan 2015, 9:01 pm

I'm restoring one of these generators. Having replaced the SenTerCel rectifier with a 1N4007 diode and reformed the smoothing caps, the HT is sitting at about 68V DC. This is the same as amornummi saw.

C1 which sits directly across the HT winding of the mains transformer is only rated at 150V, so I wouldn't expect the HT to be particularly high.

The real test will come when I measure the RF output voltage.

R2 in my SG is 3.3K and looks to be original, but the parts list says it should be 560R.

Station X · 14th Jan 2015, 5:16 pm

Some test results with 68V DC HT.

Audio output 10.6V RMS at 384Hz into open circuit. Spec 8V at 400Hz.

RF output checked across 75R load. Spec 100mV RMS on all ranges.

Range A. Unable to measure on a 20MHz scope.
Range B. 127mV RMS at 20MHz.
Range C. 141mV RMS at 10MHz.
Range D. 148mV RMS at 3MHz.
Range E. 127mV RMS at 1MHz.
Range F. 162mV RMS at 300kHz.

Modulation depth on 2MHz RF signal 28%. Spec 30%.

So I conclude that 68V DC HT is adequate.

Ozzie41bob · 21st Aug 2015, 11:14 am

Hi, just about completed restoration of one of these P1 units that someone with a blue and white striped apron has been at. I found R2 as per "Station X" was not what the manual describes, mine had what appeared to be an original 2K7 but also had a 5uF electro across it, I found this unusual for an oscillator so removed it and the oscillator stopped. Then R2 was returned to 560R and it fired up, so I have no idea why there appears to have been a factory mod to change this value. I also found the output attenuator had been blown up, all the resistors on the rear wafer were destroyed, the wafer was not all that well either. Note that the manual does not reflect the situation of two wafers or the shield between them. I am completing a revised circuit diagram for this part of the circuit.

30th Nov 2011, 3:32 am	#1
Ebrew567 Retired Dormant Member Join Date: Jul 2009 Location: Lower Hutt, Wellington, New Zealand. Posts: 19	Advance P1 Sig gen - What HT Voltage? Hi, A previous owner has replaced the power transformer and PSU with a new concoction. I can have an HT voltage from 135 to 185 Volts DC (as measured at the second electrolytic smoothing condenser), by changing transformer taps (another story). The unit has had extensive replacement of old caps, electros and composition resistors (I'm still completing that). What HT voltage should I aim for? Thanks

30th Nov 2011, 8:12 pm	#2
WME_bill Octode Join Date: Oct 2007 Location: Exeter, Devon, UK. Posts: 1,554	Re: Advance P1 Sig gen - What HT Voltage? Advance P1. I have never seen a manual. Produced about the same time as the E2, which followed the Q1 and B4 models. All very much the same in performance. Must have been some marketing idea, or special models for the Military. But the usual oscillator valve for these models was 6J6 or 12AT7. Run them between 150 and 200V I suggest, the 135v may be a bit low. If you cannot get enough RF at max output, or it fails on the highest frequency, change the valve and/or increase the voltage. I suggest it is not very critical. Bill m0wpn

2nd Dec 2011, 4:42 pm	#3
BobGreen Retired Dormant Member Join Date: Jan 2011 Location: Egham, Surrey, UK. Posts: 219	Re: Advance P1 Sig gen - What HT Voltage? The Advance E1 was like this - https://www.vintage-radio.net/forum/...6&d=1301076100

9th Dec 2011, 3:30 am	#4
Ebrew567 Retired Dormant Member Join Date: Jul 2009 Location: Lower Hutt, Wellington, New Zealand. Posts: 19	Re: Advance P1 Sig gen - What HT Voltage? Hi, Thanks to the people who came back. I increased the volts a bit to 140Vdc, I'm sure it should be higher, but its working fine on all bands and will be put to work as is (until I get around to it again). Appreciated if WME Bill would send me a PM (Re his info on Avo AFM2)

27th Jun 2012, 10:01 pm	#6
amornummi Triode Join Date: Mar 2008 Location: Huddersfield, West Yorkshire, UK. Posts: 45	Re: Advance P1 Sig gen - What HT Voltage? I have recently inherited a P-1 . Very clean , ex college. Mains input 250 volts. Heater volts 7.2 . HT winding giving 57 volts. Measures 135 ohms. Ht after silicon diode is 68 volts. Audio out 20 volts peak. RF out at 3.5 megs is bit low at minus 10 Dbm.Works happily on all freq ranges to 100+ megs Tempted to fit doubler to get a bit more output, an lose some lt to 6.3 v.

13th Jan 2015, 9:01 pm	#7
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,286	Re: Advance P1 Sig gen - What HT Voltage? I'm restoring one of these generators. Having replaced the SenTerCel rectifier with a 1N4007 diode and reformed the smoothing caps, the HT is sitting at about 68V DC. This is the same as amornummi saw. C1 which sits directly across the HT winding of the mains transformer is only rated at 150V, so I wouldn't expect the HT to be particularly high. The real test will come when I measure the RF output voltage. R2 in my SG is 3.3K and looks to be original, but the parts list says it should be 560R. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

14th Jan 2015, 5:16 pm	#8
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,286	Re: Advance P1 Sig gen - What HT Voltage? Some test results with 68V DC HT. Audio output 10.6V RMS at 384Hz into open circuit. Spec 8V at 400Hz. RF output checked across 75R load. Spec 100mV RMS on all ranges. Range A. Unable to measure on a 20MHz scope. Range B. 127mV RMS at 20MHz. Range C. 141mV RMS at 10MHz. Range D. 148mV RMS at 3MHz. Range E. 127mV RMS at 1MHz. Range F. 162mV RMS at 300kHz. Modulation depth on 2MHz RF signal 28%. Spec 30%. So I conclude that 68V DC HT is adequate. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

21st Aug 2015, 11:14 am	#9
Ozzie41bob Diode Join Date: Aug 2015 Location: Melbourne, Australia Posts: 1	Re: Advance P1 Sig gen - What HT Voltage? Hi, just about completed restoration of one of these P1 units that someone with a blue and white striped apron has been at. I found R2 as per "Station X" was not what the manual describes, mine had what appeared to be an original 2K7 but also had a 5uF electro across it, I found this unusual for an oscillator so removed it and the oscillator stopped. Then R2 was returned to 560R and it fired up, so I have no idea why there appears to have been a factory mod to change this value. I also found the output attenuator had been blown up, all the resistors on the rear wafer were destroyed, the wafer was not all that well either. Note that the manual does not reflect the situation of two wafers or the shield between them. I am completing a revised circuit diagram for this part of the circuit.