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HP-1421A Q109 Voltages

n4buq All Messages By This Member #143062 Does anyone have a readable schematic for the A101 board in a 1421A? I have a paper manual on order but until that arrives, I would appreciate finding out the voltages shown for Q109 (Page 5-16, Figure 5-9). From what I can tell, the online scan appears to show: C: +48V B: -8.8V E: -9.4V The value for B is particularly blurry but would like to know for sure what all of those are. Thanks, Barry - N4BUQ
ChuckA All Messages By This Member #143063 Here's a clean scan of the section you are looking at. ChuckA toggle quoted message Show quoted text On 3/29/2024 3:16 PM, n4buq wrote: Does anyone have a readable schematic for the A101 board in a 1421A? I have a paper manual on order but until that arrives, I would appreciate finding out the voltages shown for Q109 (Page 5-16, Figure 5-9). From what I can tell, the online scan appears to show: C: +48V B: -8.8V E: -9.4V The value for B is particularly blurry but would like to know for sure what all of those are. Thanks, Barry - N4BUQ -- See Early TV at: www.myvintagetv.com 1421A_pg5-16.jpg
n4buq All Messages By This Member #143065 Chuck, Thank you so much for that. I couldn't tell if that was a + or a - in front of the base voltage but that shows it clearly as +. Thanks again, Barry - N4BUQ toggle quoted message Show quoted text ----- Original Message ----- From: "ChuckA" <chuck@...> To: "HP-Agilent-Keysight-equipment" <[email protected]> Sent: Friday, March 29, 2024 2:38:15 PM Subject: Re: [HP-Agilent-Keysight-equipment] HP-1421A Q109 Voltages Here's a clean scan of the section you are looking at. ChuckA On 3/29/2024 3:16 PM, n4buq wrote: Does anyone have a readable schematic for the A101 board in a 1421A? I have a paper manual on order but until that arrives, I would appreciate finding out the voltages shown for Q109 (Page 5-16, Figure 5-9). From what I can tell, the online scan appears to show: C: +48V B: -8.8V E: -9.4V The value for B is particularly blurry but would like to know for sure what all of those are. Thanks, Barry - N4BUQ -- See Early TV at: www.myvintagetv.com
Hugh Gilbert All Messages By This Member #143067 -8.8V seems much more plausible, with the emitter -9.4V Hugh Gilbert toggle quoted message Show quoted text On Fri, Mar 29, 2024 at 4:02?PM n4buq <n4buq@...> wrote: Chuck, Thank you so much for that.? I couldn't tell if that was a + or a - in front of the base voltage but that shows it clearly as +. Thanks again, Barry - N4BUQ ----- Original Message ----- > From: "ChuckA" <chuck@...> > To: "HP-Agilent-Keysight-equipment" <[email protected]> > Sent: Friday, March 29, 2024 2:38:15 PM > Subject: Re: [HP-Agilent-Keysight-equipment] HP-1421A Q109 Voltages > Here's a clean scan of the section you are looking at. > > ChuckA > > On 3/29/2024 3:16 PM, n4buq wrote: >> Does anyone have a readable schematic for the A101 board in a 1421A?? I have a >> paper manual on order but until that arrives, I would appreciate finding out >> the voltages shown for Q109 (Page 5-16, Figure 5-9).? From what I can tell, the >> online scan appears to show: >> >> C: +48V >> B: -8.8V >> E: -9.4V >> >> The value for B is particularly blurry but would like to know for sure what all >> of those are. >> >> Thanks, >> Barry - N4BUQ >> >> >> >> >> >> > > -- > See Early TV at: > > > > > >
n4buq All Messages By This Member #143068 That's what I kept thinking - especially since everything else that's connected to the base is negative.? Could that be a typo? Barry - N4BUQ toggle quoted message Show quoted text -8.8V seems much more plausible, with the emitter -9.4V Hugh Gilbert On Fri, Mar 29, 2024 at 4:02?PM n4buq <n4buq@...> wrote: Chuck, Thank you so much for that.? I couldn't tell if that was a + or a - in front of the base voltage but that shows it clearly as +. Thanks again, Barry - N4BUQ ----- Original Message ----- > From: "ChuckA" <chuck@...> > To: "HP-Agilent-Keysight-equipment" <[email protected]> > Sent: Friday, March 29, 2024 2:38:15 PM > Subject: Re: [HP-Agilent-Keysight-equipment] HP-1421A Q109 Voltages > Here's a clean scan of the section you are looking at. > > ChuckA > > On 3/29/2024 3:16 PM, n4buq wrote: >> Does anyone have a readable schematic for the A101 board in a 1421A?? I have a >> paper manual on order but until that arrives, I would appreciate finding out >> the voltages shown for Q109 (Page 5-16, Figure 5-9).? From what I can tell, the >> online scan appears to show: >> >> C: +48V >> B: -8.8V >> E: -9.4V >> >> The value for B is particularly blurry but would like to know for sure what all >> of those are. >> >> Thanks, >> Barry - N4BUQ >> >> >> >> >> >> > > -- > See Early TV at: > > > > > >
Ozan All Messages By This Member #143069 HP has almost the same exact circuit with -8.5V in one state (lamp is on) and -11.4V (lamp is off) in another state. Looking at 1421 schematic, few voltages look like typos.? Ozan ? toggle quoted message Show quoted text On Fri, Mar 29, 2024 at 01:50 PM, Hugh Gilbert wrote: -8.8V seems much more plausible, with the emitter -9.4V ? Hugh Gilbert On Fri, Mar 29, 2024 at 4:02?PM n4buq <n4buq@...> wrote: Chuck, Thank you so much for that.? I couldn't tell if that was a + or a - in front of the base voltage but that shows it clearly as +. Thanks again, Barry - N4BUQ ----- Original Message ----- > From: "ChuckA" <chuck@...> > To: "HP-Agilent-Keysight-equipment" <[email protected]> > Sent: Friday, March 29, 2024 2:38:15 PM > Subject: Re: [HP-Agilent-Keysight-equipment] HP-1421A Q109 Voltages > Here's a clean scan of the section you are looking at. > > ChuckA > > On 3/29/2024 3:16 PM, n4buq wrote: >> Does anyone have a readable schematic for the A101 board in a 1421A?? I have a >> paper manual on order but until that arrives, I would appreciate finding out >> the voltages shown for Q109 (Page 5-16, Figure 5-9).? From what I can tell, the >> online scan appears to show: >> >> C: +48V >> B: -8.8V >> E: -9.4V >> >> The value for B is particularly blurry but would like to know for sure what all >> of those are. >> >> Thanks, >> Barry - N4BUQ >> >> >> >> >> >> > > -- > See Early TV at: > > > > > >
Ozan All Messages By This Member #143070 Copy/paste didn't work. HP 1821 has almost the same circuit. Ozan === toggle quoted message Show quoted text On Fri, Mar 29, 2024 at 02:05 PM, Ozan wrote: HP has almost the same exact circuit with -8.5V in one state (lamp is on) and -11.4V (lamp is off) in another state. Looking at 1421 schematic, few voltages look like typos.? Ozan ? On Fri, Mar 29, 2024 at 01:50 PM, Hugh Gilbert wrote: -8.8V seems much more plausible, with the emitter -9.4V ? Hugh Gilbert On Fri, Mar 29, 2024 at 4:02?PM n4buq <n4buq@...> wrote: Chuck, Thank you so much for that.? I couldn't tell if that was a + or a - in front of the base voltage but that shows it clearly as +. Thanks again, Barry - N4BUQ ----- Original Message ----- > From: "ChuckA" <chuck@...> > To: "HP-Agilent-Keysight-equipment" <[email protected]> > Sent: Friday, March 29, 2024 2:38:15 PM > Subject: Re: [HP-Agilent-Keysight-equipment] HP-1421A Q109 Voltages > Here's a clean scan of the section you are looking at. > > ChuckA > > On 3/29/2024 3:16 PM, n4buq wrote: >> Does anyone have a readable schematic for the A101 board in a 1421A?? I have a >> paper manual on order but until that arrives, I would appreciate finding out >> the voltages shown for Q109 (Page 5-16, Figure 5-9).? From what I can tell, the >> online scan appears to show: >> >> C: +48V >> B: -8.8V >> E: -9.4V >> >> The value for B is particularly blurry but would like to know for sure what all >> of those are. >> >> Thanks, >> Barry - N4BUQ >> >> >> >> >> >> > > -- > See Early TV at: > > > > > >
factory All Messages By This Member #143071 The 1821A is very similar for the reset lamp circuit, the voltages are negative on the base, picture below is from the repair of my 1821A, the lamp had failed in that one. David
n4buq All Messages By This Member #143092 I got a chance to test the circuit just a bit.? I placed a 47k resistor between the base of Q109 and ground.? That caused the lamp to illuminate so the transistor is still good.? I just need to determine why the base voltage is being held at or below the emitter voltage. Thanks, Barry - N4BUQ toggle quoted message Show quoted text That's what I kept thinking - especially since everything else that's connected to the base is negative.? Could that be a typo? Barry - N4BUQ -8.8V seems much more plausible, with the emitter -9.4V Hugh Gilbert On Fri, Mar 29, 2024 at 4:02?PM n4buq <n4buq@...> wrote: Chuck, Thank you so much for that.? I couldn't tell if that was a + or a - in front of the base voltage but that shows it clearly as +. Thanks again, Barry - N4BUQ ----- Original Message ----- > From: "ChuckA" <chuck@...> > To: "HP-Agilent-Keysight-equipment" <[email protected]> > Sent: Friday, March 29, 2024 2:38:15 PM > Subject: Re: [HP-Agilent-Keysight-equipment] HP-1421A Q109 Voltages > Here's a clean scan of the section you are looking at. > > ChuckA > > On 3/29/2024 3:16 PM, n4buq wrote: >> Does anyone have a readable schematic for the A101 board in a 1421A?? I have a >> paper manual on order but until that arrives, I would appreciate finding out >> the voltages shown for Q109 (Page 5-16, Figure 5-9).? From what I can tell, the >> online scan appears to show: >> >> C: +48V >> B: -8.8V >> E: -9.4V >> >> The value for B is particularly blurry but would like to know for sure what all >> of those are. >> >> Thanks, >> Barry - N4BUQ >> >> >> >> >> >> > > -- > See Early TV at: > > > > > >

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