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7623A Storage problem
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Would you believe that I have a 7CT1N curve-tracer, but of course nit
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operates in the 7623A mainframe, which isn't working? I don't have another 7000-series mainframe, sadly. Colin. -----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Thomas Garson Sent: 04 October 2020 22:37 To: [email protected] Subject: Re: [TekScopes] 7623A Storage problem The junctions of that type of counterfeit power transistor will have a higher forward voltage than a genuine part. Usually they read as much as .1 to .15 volts higher on a typical DMMs diode test range. They will also have different junction capacitance. I can't give numbers as I'm not where I have proper tools. However a data sheet for the McCoy will provide at least some of that information. A curve tracer will reveal a lot. Small signal transistors have very different family of curves than most any power transistor. While the Tek curve tracers are the tool of choice, I've gotten a lot of good mileage from the Heathkit variety. The Heathkit curve tracer, which does not have a display, will work with any DC coupled 'scope and can sometimes be found on eBay for a low price that belies its usefulness. Even if broken, they are relatively simple and easy for a moderately knowledgeable tech to fix. Thomas Garson Aural Technology, Ashland, OR By my calculation, the dynamic range of the universe is roughly 679dB, which is approximately 225 bits, collected at a rate 1.714287514x10^23 sps. On 10/4/20 12:59 PM, Tom Lee wrote: There are also notorious Chinese knock-offs which contain low-power |
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It appears that I am a nit. I means to type "it" and a gremlin made me add
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an "n" to the beginning. Sorry. -----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Colin Herbert via groups.io Sent: 07 October 2020 14:23 To: [email protected] Subject: Re: [TekScopes] 7623A Storage problem Would you believe that I have a 7CT1N curve-tracer, but of course nit operates in the 7623A mainframe, which isn't working? I don't have another 7000-series mainframe, sadly. Colin. -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Thomas Garson Sent: 04 October 2020 22:37 To: [email protected] Subject: Re: [TekScopes] 7623A Storage problem The junctions of that type of counterfeit power transistor will have a higher forward voltage than a genuine part. Usually they read as much as .1 to .15 volts higher on a typical DMMs diode test range. They will also have different junction capacitance. I can't give numbers as I'm not where I have proper tools. However a data sheet for the McCoy will provide at least some of that information. A curve tracer will reveal a lot. Small signal transistors have very different family of curves than most any power transistor. While the Tek curve tracers are the tool of choice, I've gotten a lot of good mileage from the Heathkit variety. The Heathkit curve tracer, which does not have a display, will work with any DC coupled 'scope and can sometimes be found on eBay for a low price that belies its usefulness. Even if broken, they are relatively simple and easy for a moderately knowledgeable tech to fix. Thomas Garson Aural Technology, Ashland, OR By my calculation, the dynamic range of the universe is roughly 679dB, which is approximately 225 bits, collected at a rate 1.714287514x10^23 sps. On 10/4/20 12:59 PM, Tom Lee wrote: There are also notorious Chinese knock-offs which contain low-power |
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I am a bit puzzled as to how I gain access to Q1195 and other parts on the HV board. I can see where it is located on the shield of the HV compartment, but how do I get access to it? I have removed the A12 low-voltage regulator board and the fan assembly, but the manual then tells me to disconnect various things including the CRT base socket, the CRT anode plug and the multi-pin connectors on the A8 Z-axis board. It then says that there is one screw on the bottom of the high-voltage compartment and two screws at the top to release it from the chassis. Since the Z-axis board is still attached to the high-voltage compartment, as also is the A13 readout board, this puzzles me. I cannot see the screws which hold the high-voltage compartment in place and some of the multi-pin connectors on the Z-axis board are obscured by the casing of the scope. I can also see two high-voltage connections to the CRT, one on either side of the scope. Which one is the anode connector?
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TIA again, Colin. -----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Miguel Work Sent: 25 September 2020 21:13 To: [email protected] Subject: Re: [TekScopes] 7623A Storage problem I remember that is mounted in the HV metallic shield/box -----Mensaje original----- De: [email protected] [mailto:[email protected]] En nombre de Colin Herbert via groups.io Enviado el: viernes, 25 de septiembre de 2020 18:47 Para: [email protected] Asunto: Re: [TekScopes] 7623A Storage problem I have found that F814 (2A) on the LV power supply was blown and continues to do so, possibly because of a failure of Q1195 or C1198 (47uF). My question is how can I get to either of these components? I can see from the Manual that C1198 is on the HV board and that I might have to get in there to look at it. But Q1195 isn't on the HV board because it is heatsinked, but where is it located? I have a transistor checker and can thus check it out, if I can locate it. Colin. -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Roger Evans via groups.io Sent: 23 September 2020 14:43 To: [email protected] Subject: Re: [TekScopes] 7623A Storage problem Colin, I had the afterthought about low voltages since the regulation of the power transistor Q1195 relies on +5V, +15V and +130V being OK. The components I mentioned are all on the low voltage side of the transformer T1199 and can be checked with the power off. Q1195 is attached by a plug and socket so it can effectively be tested out of circuit, Q1190 can be checked as a pair of diodes for open circuit / short circuit. The two capacitors are likely to be short circuit if they have failed and L1198 will be open circuit if the fuse didn't do its job in time. At least you don't have to wait 30 minutes for the high voltage to leak away! Regards, Roger |
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OK, I have loosened/removed what I think are the correct screws/CRT base/anode connector/multipin connectors and the casing seems to be loose. However, it is proving to be a problem getting that whole assembly away from the HV board. I realise that the manual suggests care, to avoid damage to pin connectors and components, but does anyone who has experience of this have any hints as to how to go about it? Surely I cannot be the first to gain access to this HV board? It seems as though plug P1196 is nearly in view, but is being rather shy!
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TIA, Colin. -----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Colin Herbert via groups.io Sent: 12 October 2020 16:27 To: [email protected] Subject: Re: [TekScopes] 7623A Storage problem I am a bit puzzled as to how I gain access to Q1195 and other parts on the HV board. I can see where it is located on the shield of the HV compartment, but how do I get access to it? I have removed the A12 low-voltage regulator board and the fan assembly, but the manual then tells me to disconnect various things including the CRT base socket, the CRT anode plug and the multi-pin connectors on the A8 Z-axis board. It then says that there is one screw on the bottom of the high-voltage compartment and two screws at the top to release it from the chassis. Since the Z-axis board is still attached to the high-voltage compartment, as also is the A13 readout board, this puzzles me. I cannot see the screws which hold the high-voltage compartment in place and some of the multi-pin connectors on the Z-axis board are obscured by the casing of the scope. I can also see two high-voltage connections to the CRT, one on either side of the scope. Which one is the anode connector? TIA again, Colin. -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Miguel Work Sent: 25 September 2020 21:13 To: [email protected] Subject: Re: [TekScopes] 7623A Storage problem I remember that is mounted in the HV metallic shield/box -----Mensaje original----- De: [email protected] [mailto:[email protected]] En nombre de Colin Herbert via groups.io Enviado el: viernes, 25 de septiembre de 2020 18:47 Para: [email protected] Asunto: Re: [TekScopes] 7623A Storage problem I have found that F814 (2A) on the LV power supply was blown and continues to do so, possibly because of a failure of Q1195 or C1198 (47uF). My question is how can I get to either of these components? I can see from the Manual that C1198 is on the HV board and that I might have to get in there to look at it. But Q1195 isn't on the HV board because it is heatsinked, but where is it located? I have a transistor checker and can thus check it out, if I can locate it. Colin. -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Roger Evans via groups.io Sent: 23 September 2020 14:43 To: [email protected] Subject: Re: [TekScopes] 7623A Storage problem Colin, I had the afterthought about low voltages since the regulation of the power transistor Q1195 relies on +5V, +15V and +130V being OK. The components I mentioned are all on the low voltage side of the transformer T1199 and can be checked with the power off. Q1195 is attached by a plug and socket so it can effectively be tested out of circuit, Q1190 can be checked as a pair of diodes for open circuit / short circuit. The two capacitors are likely to be short circuit if they have failed and L1198 will be open circuit if the fuse didn't do its job in time. At least you don't have to wait 30 minutes for the high voltage to leak away! Regards, Roger |
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