Hello Mark,
OK... so Q1486 is an original Tek (as it has the Tek part number) and it's checking OK... This is better news than worse... even though it's one less explanation for the problem, at least it's an original one which is a great relief, since it being anything else would sure mean bigger problems (to find one that would work).
As innocent as Q1486 is (being a low frequency transistor), the problem in this circuit is the circuit itself... From what I learnt on my own 464 issue, which David Hess was so kind of walking me through, the circuit is so finnicky that it's more likely for it to not work than it is likely to work.
That said, the "critical" element in it is Q1486 having its parameters just right (not a matter of being outstanding, nor poor, but just right)... and that is what you get when you have the correct Q1486 part number (which you got, bingo!).
Now, while the transistor is the correct one (and seems to be in working order), it's still true that the circuit is finnicky and works very marginally, so it doesn't take much for it to not work.
If it would be me, I would start by disconnecting from T1501, everything that's not strictly necessary for the H.V. regulation feedback loop to work...Namely:
1. The output to the voltage doubler (the whole voltage doubler board that is on the side of the 464.
2. The diode that recitfies the +600V that goes to the Storage board (and keep the NON STORE button pressed).
There's no harm in operating the scope without either of those voltages. Without the voltage doubler there won't be 7kV of Post Deflection Acceleration, but as I was once thaught, the CRT would still work (although very dim and with a wrong deflection factor).
That's for a start... and when I have the schematics at hand, I can think of something else to try.
Rgrds,
Fabio
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On Thu, Aug 23, 2018 at 11:52 AM, <kickingypsy9@...> wrote:
i did check Q1486 first time around, its a rca but it also has 151-0140 on it
..dont know if its original but it checks ok.i also cleaned the place where
the wire hooks to it. i took the rca out, and put a 2SC3280 in, and just
soldered it the board to see if it would run.....hooked up my scope to pin 3
and powered it up...wow its running,went to see if i could see any
display,nothing,checked again ,it stoped running.one thing i noticed when i
powered it off the crt light completly up then faded to a dot in the center.so
i know the hv came up for a moment.puled out my transister it still checks
ok.i still have Q1492 the protect trans out of circuit.so...i either have a
intermitted T1501 or somthing weired going on with that oscillator circuit.i
tried freezing and heating the board,no change. i tend to think its the
circuit,i dont see why that output should be anything speacial.its just a
115wat medium speed audio output.but still changing it made it work for a
second ???what the hecks going on here!!!
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On Thu, Aug 23, 2018, 12:42 <hfran@...> wrote: 454 worked fine, but had a stalled fan, which I replaced by a 12 VDC fan,
which I supplied from +12v unregulated. But then no trace anymore.
1) HV oscillator does not oscillate. Checked Q1414, G1413, Q1423 and Q
1430 by diode check. All appear to be working, except Q1430 might have too
low hfe, where I cannot be sure by diode check.
2) failure to oscillate could also come from too much loading. I fed
-30v via 1 MOhm to TP1469
( -1960V, when working ) and measured 25 microamp to GND, meaning a leak
resistor from possibly only 200k to GND. Could such a leak current be
normal ? C1469 and C1479 ( unsoldered ) are
( low voltage ) multimeter- measured o.k.
Since there could be many caps and diodes defective I would need a
strategy to follow, because to replace Q1430 is complicated and might still
not cure the failure.
Has anybody experienced such a failure or has some idea or strategy.That
would be extremely helpful.
What happens if you temporarily disconnect the fan and power up for a short period of time? Maybe the new fan is drawing too much from the circuit? Mark
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454 worked fine, but had a stalled fan, which I replaced by a 12 VDC fan, which I supplied from +12v unregulated. But then no trace anymore.
1) HV oscillator does not oscillate. Checked Q1414, G1413, Q1423 and Q 1430 by diode check. All appear to be working, except Q1430 might have too low hfe, where I cannot be sure by diode check.
2) failure to oscillate could also come from too much loading. I fed -30v via 1 MOhm to TP1469
( -1960V, when working ) and measured 25 microamp to GND, meaning a leak resistor from possibly only 200k to GND. Could such a leak current be normal ? C1469 and C1479 ( unsoldered ) are
( low voltage ) multimeter- measured o.k.
Since there could be many caps and diodes defective I would need a strategy to follow, because to replace Q1430 is complicated and might still not cure the failure.
Has anybody experienced such a failure or has some idea or strategy.That would be extremely helpful.
|
i did check Q1486 first time around, its a rca but it also has 151-0140 on it ..dont know if its original but it checks ok.i also cleaned the place where the wire hooks to it. i took the rca out, and put a 2SC3280 in, and just soldered it the board to see if it would run.....hooked up my scope to pin 3 and powered it up...wow its running,went to see if i could see any display,nothing,checked again ,it stoped running.one thing i noticed when i powered it off the crt light completly up then faded to a dot in the center.so i know the hv came up for a moment.puled out my transister it still checks ok.i still have Q1492 the protect trans out of circuit.so...i either have a intermitted T1501 or somthing weired going on with that oscillator circuit.i tried freezing and heating the board,no change. i tend to think its the circuit,i dont see why that output should be anything speacial.its just a 115wat medium speed audio output.but still changing it made it work for a second ???what the hecks going on here!!!
|
scanned: Common Parts Design Catalog #5, Resistors and Capacitors, March 1989
This scan was made possible by Pete Lancashire.
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Hello Fabio
I've taken apart the TG501 and had a closer look. There are only three socketed chips - U310, U300 and U290. U310 is part of the first divide by 5 counter. I think the sockets are the dodgy TI version, so took all three chips out cleaned the pins and replaced them, but no change.
Also checked the 100MHz PLL at its output points (U290D) Both pins 9 (going to U310A in the divide by 5 counter) and 15 (going to U290C in the 5ns section) show exactly 80MHz. So as you suggested, it looks like the divide by 5 counter is the problem and I'll start by replacing U310, once I get hold of another MC 10131.
It also looks like this particular TG501 was originally configured for 10 MHz external reference oscillator, but has been changed back to the internal 1 MHz reference. All the changes seem to have been done according to the manual and I've anyway checked and adjusted the 1 MHz oscillator so that it is correct.
Thanks again for your help on this.
Regards
Kerry
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Re: Tek 371a test bed needed??? Or not
Hi Oliver,
It appears that the 371A will accept one adapter. The 371A is designed with Kelvin connectors for the three transistor leads so it has 6 banana sockets in all.
The adapters for the 575 are not Kelvin so they only have three banana plugs. These three plugs would plug into the left three banana sockets in the 371A and let you measure the device parameter but without the accuracy of Kelvin connectors.
The adapters for the 576 and 577 curve tracers have 5 banana plugs. This is because they use Kelvin connectors for the high current leads of a transistor (emitter and collector, or source and drain) but the Tek engineers decided the base (gate) didn't require the Kelvin connector. These adapters can be used in the 371A and take advantage of the Emitter and Collector Kelvin contacts. The Base contact will not be Kelvin. These 576 and 577 adapters would plug into the first and second vertical row of banana sockets.
The 371A adapters have all six banana plugs and the E, B, and C (S, G, D) connections are Kelvin.
Dennis Tillman W7PF
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-----Original Message-----
From: oliver> johnson via Groups.Io
Sent: Wednesday, August 22, 2018 2:31 PM
Subject: [TekScopes] Tek 371a test bed needed??? Or not
I am not sure why i am asking , the tek 371a curve tracer , dose it need
the test unit or can you use the same adapter that the 576 uses . Is there
something special about test rig or just a clean way to test items with
shield ???? -- Dennis Tillman W7PF TekScopes Moderator
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Re: scanned: Common Parts Design Catalog #2, Mechanical, June 1983
Here is the November 1988 revision of the Mechanical parts catalog:
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Tek 371a test bed needed??? Or not
I am not sure why i am asking , the tek 371a curve tracer , dose it need the test unit or can you use the same adapter that the 576 uses . Is there something special about test rig or just a clean way to test items with shield ????
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Re: scanned: Common Parts Design Catalog #2, Mechanical, June 1983
Pete and Kurt -
Thank you both for the parts catalogs. Prior to those posts all that I had was the Oct-1982 semiconductors catalog and the knobs section of the mechanical catalog. Your posts will be a great help in keeping vintage Tek instruments working.
Dale H. Cook, GR/HP/Tek Collector, Roanoke/Lynchburg, VA
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Hello Mark,
Thousand apologies... I went through the past message replying to one thing you said, but thinking you said something else.
What I meant (about checking whether it was a Tek original transistor or not) was to check Q1486 (the power transistor that's off-board, connected by wires).
This is the one (Q1486) which I got burnt (on my 464) and is the one I learnt is tricky to replace and, therefore the one that, should it not be a original Tek 151-0140-00, might be the cause for your oscillator not working.
About injecting the signal... well, even if you could do it...it wouldn't tell 100% sure that the transformer is OK, but could help give you some hint that it IS NOT.
The generator I used was a very simple one, using one port of an HC Schmitt Trigger (74HC14) as an oscillator (with a resistor and capacitor to set the frequency). This one port driving all the other 5 ports in parallel (to increase current drive) and feeding the signal, through a series resistor into the transformer's primary (having both ends disconnected, from the transistor and from the +V side).
Regarding your question on horizontal drive waveforms...
Yes, should the rest of the scope be working, and assuming that all horizontal controls are set correctly (i.e. Horizontal Display set to "A", Triggering mode set to "AUTO" and A&B sweep dials set to a sweep rate that you can measure, "X10" button out and horizontal position pots at center, and the "NON STORE" button is pressed), you should see opposite voltage ramps on the horizontal plates of the CRT.
Rgrds,
Fabio
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On Wed, Aug 22, 2018 at 03:12 PM, <kickingypsy9@...> wrote:
i checked Q1484 it is origanal 151-0136-00 is on the trans.i dont have the
capability to inject a 30khz signal into hv transformer.besides it is not
going neg or starting to run with it out.forgetting about the hv for a minuet,
i got to wondering if there is any horz or vert waveformes even without the hv
working. i cant find any horz drive waves.even with no inputs shouldnt there
still be horz drive waves?
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i checked Q1484 it is origanal 151-0136-00 is on the trans.i dont have the capability to inject a 30khz signal into hv transformer.besides it is not going neg or starting to run with it out.forgetting about the hv for a minuet, i got to wondering if there is any horz or vert waveformes even without the hv working. i cant find any horz drive waves.even with no inputs shouldnt there still be horz drive waves?
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Re: scanned: Common Parts Design Catalog #2, Mechanical, June 1983
Thank you Pete and Kurt!!!
Vince.
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On 08/22/2018 09:43 AM, Kurt Rosenfeld wrote: This scan was made possible by Pete Lancashire.
--
Michigan VHF Corp.
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Re: scanned: Common Parts Design Catalog #2, Mechanical, June 1983
Thanks very much indeed - very useful when needed
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Re: scanned: Common Parts Design Catalog #2, Mechanical, June 1983
Try
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On 22 Aug 2018, at 14:54, tom jobe <tomjobe@...> wrote:
Thank you Kurt and Pete!
I fretted that I had somehow missed #2, but now it has shown up.
These are excellent scans of excellent information!
tom jobe...
On 8/22/2018 6:43 AM, Kurt Rosenfeld wrote:
This scan was made possible by Pete Lancashire.
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Re: scanned: Common Parts Design Catalog #2, Mechanical, June 1983
I can't get to proxy.w140.com as the ISP blocks my VPN provider.
Could you provide another DL location please.
Thanks
David
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-----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of Kurt Rosenfeld Sent: 22 August 2018 14:43 To: [email protected]Subject: [TekScopes] scanned: Common Parts Design Catalog #2, Mechanical, June 1983 This scan was made possible by Pete Lancashire.
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Re: scanned: Common Parts Design Catalog #2, Mechanical, June 1983
Thank you Kurt and Pete!
I fretted that I had somehow missed #2, but now it has shown up.
These are excellent scans of excellent information!
tom jobe...
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On 8/22/2018 6:43 AM, Kurt Rosenfeld wrote: This scan was made possible by Pete Lancashire.
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scanned: Common Parts Design Catalog #2, Mechanical, June 1983
This scan was made possible by Pete Lancashire.
|
Thanks but priced way too high and too much negative feedback for me
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On Aug 21, 2018, at 1:28 AM, Velik Kazakov via Groups.Io <velik_kazakov@...> wrote:
Have one on ebay
On 18 Aug 2018, at 18:19, n9llo via Groups.Io <N9LLO@...> wrote:
120-1087-00 transformer or complete HV module for a 7603.
Chris
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Re: scanned: Common Parts Design Catalog #3, Materials, April 1989
The gems keep coming! My thanks to all concerned who are making this superb reference library
available - hats off!
Craig
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This scan was made possible by Pete Lancashire.
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Fabio Trevisan
Dale H. Cook
David C. Partridge