Re: I built a TM500 mainframe tester, and updated the design. Someone might find this useful?
I would also like a set of boards. Thank you for the great project, for the time you spent, and for the clever mechanical and electrical engineering.
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Re: Peter Keller's Book Mailing Status
Let¡¯s see¡.
Dennis¡¯s time of xxx hours times a $50.00 hourly rate to do all of this equals $xxxx.xx.
Although it is only one book for me you have put in a monumental effort to get all of this done. What is your next feat? Walking a tightrope between two high rise buildings, putting on a jet pack and flying through the Grand Canyon from one end to the other or traveling across the country in a lawn chair attached to helium filled balloons???
Greg
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Re: A question from the unwashed relative to: I built a TM500 mainframe tester, and updated the design. Someone might find this useful?
On Fri, Jan 1, 2021 at 11:02 PM, EJP wrote:
I have an FG504 and such a TM504 that I had to correct the phasing on.
If you might indulge a few inquiries... Did incorrect phasing damage the FG504? Is that something you did to the TM504?... or was it miswired at the factory... or during a "repair, someone else?" Do you know... was the TM504... and early manufacture... or a later one?
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Re: A question from the unwashed relative to: I built a TM500 mainframe tester, and updated the design. Someone might find this useful?
On Fri, Jan 1, 2021 at 08:47 PM, demianm_1 wrote:
I'm working on an interface board to enable powering and getting the signal
out of a Tek 7000 plugin
This had been done, many times... and there is much ink spilled about it, on this forum... and on the Web... that is... if you are mentioning about something (a cable, or board) that plugs into the connector at the back of a bay, in a 7000 frame, and then allows one to attach (and "run/test") a 7000 plug-in. To see... search this forum on "extender."
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Re: Peter Keller's Book Mailing Status
Dennis, you're a saint! Sorry that no good deed goes unpunished!
Happy New Year,
Tom
Sent from my iThing, so please forgive the terseness and typos.
toggle quoted message
Show quoted text
On Jan 2, 2021, at 12:19, "Dennis Tillman W7pF" <dennis@...> wrote: This morning I mailed 76 of Peter Keller's books. These went to 72 people in
the USA who ordered Peter's book.
At the request of our currently shorthanded post office staff I have been
asked to wait until Thursday to mail the 25 International orders when there
will be enough people on duty to process them. It takes time to verify the
address, determine the postage, and process the customs forms for each
international order.
Here is the list of domestic orders I mailed today. Because these were send
Media Mail Rate the clerk only has to enter the zip code and print out a
label for each box. It took about 1 1/2 hours to process 72 domestic orders.
There are no tracking numbers for Media Mail packages.
If you want to know if I mailed your book(s) today scan down this zip code
sorted list for your initials.
------ --- -------
01460, HV, 1 Book
01510, PE, 1 Book
01742, SB, 1 Book
02090, JY, 1 Book
04605, LS, 1 Book
06057, EO, 1 Book
06851, LK, 1 Book
07023, MD, 1 Book
10034, PC, 1 Book
11507, LL, 1 Book
13211, BG, 1 Book
13635, BL, 1 Book
14094, SW, 1 Book
14131, CD, 1 Book
15068, DM, 1 Book
17044, DK, 1 Book
18944, CA, 1 Book
19010, SH, 1 Book
19808, RD, 1 Book
20169, CL, 1 Book
20613, TK, 1 Book
20872, CH, 2 Books
20901, JD, 1 Book
22406, FD, 1 Book
23236, MV, 1 Book
27932, RB, 1 Book
28411, VS, 1 Book
29445, GL, 1 Book
30064, MM, 1 Book
30341, HO, 1 Book
32707, SB, 1 Book
32754, DD, 1 Book
32765, JR, 2 Books
45014, ES, 1 Book
45066, LS, 1 Book
45801, TL, 1 Book
48206, CW, 1 Book
48371, VV, 1 Book
48843, JR, 1 Book
56549, EN, 1 Book
59405, GM, 1 Book
66062, JF, 1 Book
67212, CC, 1 Book
72834, ML, 1 Book
78746, MA, 1 Book
80015, CD, 1 Book
80023, PB, 1 Book
80234, JM, 1 Book
80907, KP, 1 Book
87107, JG, 1 Book
87124, CM, 1 Book
87544, BD, 1 Book
89511, MM, 1 Book
91602, BH, 1 Book
92109, SP, 1 Book
92806, LM, 1 Book
94301, BC, 1 Book
94550, JR, 1 Book
94602, RD, 1 Book
94941, BH, 1 Book
94947, JP, 1 Book
95320, TN, 3 Books
95693, KS, 1 Book
97338, JG, 1 Book
97424, TP, 1 Book
98008, DM, 1 Book
98030, BL, 1 Book
98115, MH, 1 Book
98166, CN, 1 Book
98275, SJ, 1 Book
98501, DG, 1 Book
Anonymous, 1 Book
Dennis Tillman W7pF
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Re: Grid Bias Adjustment on 475A
Chuck,
Thanks for that as I did not feel qualified to make such a statement, based on my very limited knowledge of the subject. Appreciate that you have confirmed that I am not totally without a clue.
Sincerely,
--
Michael Lynch
Dardanelle, AR
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Re: Peter Keller's Book Mailing Status
Dennis,
THANK YOU. I know that we do not say this enough for all that you do to keep this group running smooth. You are GREATLY appreciated!
Sincerely,
--
Michael Lynch
Dardanelle, AR
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Re: Grid Bias Adjustment on 475A
That and perhaps what he asserts is nonsense?
The grid is most assuredly biased relative to the cathode
on this, and probably any, CRT.
-Chuck Harris
Michael W. Lynch via groups.io wrote:
toggle quoted message
Show quoted text
On Sat, Jan 2, 2021 at 01:43 PM, David Campbell wrote:
5. Possibly the main point, there is **** NO such thing as grid bias.**** No
such thing as base bias in transistors either. Control is exerted from GRID to
CATHODE. A grid cannot control the space by itself. It is an electro-static
couple with the Cathode! Base bias is meaningless without the emitter.
David,
This may be the source of confusion for those of us not as well versed in these issues. Regardless of your fine technical explanation, TEKTRONIX still calls R1375 "GRID BIAS" on the schematics. That being said, who am I to argue the point? If some EE or Designer at the place that made the instrument calls it "GRID BIAS", then for continuity we poor and less educated souls in the field tend to use that name. Right or wrong, that is the name that shows up on the schematics. Another one of the many error and omissions we find in various schematics.
I appreciate your explanation of what is supposed to go on here!
Sincerely
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Hello
Many moons ago I saw a topic on here regarding the 2230 and a storage display problem and as far as I could tell it never reached a conclusion. Unfortunately it is the problem I have now...or very similar. Therefore, I wonder if anyone has a recollection of the problem and what the solution is or was? Briefly, in storage mode BOTH traces are displayed on top of each other when 'both' are selected so it just looks like one trace. Using only channel 1, inputting a 2Vpp signal gives a perfect image BUT half the actual voltage, 1Vpp.Inputing a square wave into channel 2 same amplitude it's 25% of the voltage. Select both and the waveforms are summed giving a display that's a little of each, straight sides and rounded tops. If a 2Vpp sine is input to BOTH channels and only channel one is activated and displayed in storage then you get a 2Vpp sine wave which is what it should be. In short, it seems like there is some mixing going on of the waveform content and amplitude. Normal mode is perfect in all respects. As I recall there was a suspicion U2101 was the culprit but it was never confirmed. At the moment I have the 4 wire connection plug that goes to channel 2 on the storage board removed and the 2 signal wires earthed with jumpers. I can still use channel 1 storage and multiply the amplitude by 2 as a rough guide although it's far from accurate. Anyone remember something like this and what the cause was? Many thanks in advance.
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Peter Keller's Book Mailing Status
This morning I mailed 76 of Peter Keller's books. These went to 72 people in
the USA who ordered Peter's book.
At the request of our currently shorthanded post office staff I have been
asked to wait until Thursday to mail the 25 International orders when there
will be enough people on duty to process them. It takes time to verify the
address, determine the postage, and process the customs forms for each
international order.
Here is the list of domestic orders I mailed today. Because these were send
Media Mail Rate the clerk only has to enter the zip code and print out a
label for each box. It took about 1 1/2 hours to process 72 domestic orders.
There are no tracking numbers for Media Mail packages.
If you want to know if I mailed your book(s) today scan down this zip code
sorted list for your initials.
------ --- -------
01460, HV, 1 Book
01510, PE, 1 Book
01742, SB, 1 Book
02090, JY, 1 Book
04605, LS, 1 Book
06057, EO, 1 Book
06851, LK, 1 Book
07023, MD, 1 Book
10034, PC, 1 Book
11507, LL, 1 Book
13211, BG, 1 Book
13635, BL, 1 Book
14094, SW, 1 Book
14131, CD, 1 Book
15068, DM, 1 Book
17044, DK, 1 Book
18944, CA, 1 Book
19010, SH, 1 Book
19808, RD, 1 Book
20169, CL, 1 Book
20613, TK, 1 Book
20872, CH, 2 Books
20901, JD, 1 Book
22406, FD, 1 Book
23236, MV, 1 Book
27932, RB, 1 Book
28411, VS, 1 Book
29445, GL, 1 Book
30064, MM, 1 Book
30341, HO, 1 Book
32707, SB, 1 Book
32754, DD, 1 Book
32765, JR, 2 Books
45014, ES, 1 Book
45066, LS, 1 Book
45801, TL, 1 Book
48206, CW, 1 Book
48371, VV, 1 Book
48843, JR, 1 Book
56549, EN, 1 Book
59405, GM, 1 Book
66062, JF, 1 Book
67212, CC, 1 Book
72834, ML, 1 Book
78746, MA, 1 Book
80015, CD, 1 Book
80023, PB, 1 Book
80234, JM, 1 Book
80907, KP, 1 Book
87107, JG, 1 Book
87124, CM, 1 Book
87544, BD, 1 Book
89511, MM, 1 Book
91602, BH, 1 Book
92109, SP, 1 Book
92806, LM, 1 Book
94301, BC, 1 Book
94550, JR, 1 Book
94602, RD, 1 Book
94941, BH, 1 Book
94947, JP, 1 Book
95320, TN, 3 Books
95693, KS, 1 Book
97338, JG, 1 Book
97424, TP, 1 Book
98008, DM, 1 Book
98030, BL, 1 Book
98115, MH, 1 Book
98166, CN, 1 Book
98275, SJ, 1 Book
98501, DG, 1 Book
Anonymous, 1 Book
Dennis Tillman W7pF
|
Re: Grid Bias Adjustment on 475A
On Sat, Jan 2, 2021 at 01:43 PM, David Campbell wrote:
5. Possibly the main point, there is **** NO such thing as grid bias.**** No
such thing as base bias in transistors either. Control is exerted from GRID to
CATHODE. A grid cannot control the space by itself. It is an electro-static
couple with the Cathode! Base bias is meaningless without the emitter.
David, This may be the source of confusion for those of us not as well versed in these issues. Regardless of your fine technical explanation, TEKTRONIX still calls R1375 "GRID BIAS" on the schematics. That being said, who am I to argue the point? If some EE or Designer at the place that made the instrument calls it "GRID BIAS", then for continuity we poor and less educated souls in the field tend to use that name. Right or wrong, that is the name that shows up on the schematics. Another one of the many error and omissions we find in various schematics. I appreciate your explanation of what is supposed to go on here! Sincerely -- Michael Lynch Dardanelle, AR
|
Re: I built a TM500 mainframe tester, and updated the design. Someone might find this useful?
I also would be interested in a set of boards if they aren't too pricey.
A source of the mechanical parts is plug-ins for the 5000 series scopes e.g. 5103, 5440, which use exactly the same form factor as the TM 500/5000 plugins, but with different keying on the edge connector as they are NOT electrically compatible.
The plugins for those scopes are frequently available inexpensively as they seem to be not very popular now.
Personally I like them for the large screen (same size as the 7603) and lack of fan. The low bandwidth of the 510x is adequate for audio, I use one with my audio analyzer to monitor both audio channels as well as the distortion trace simultaneously.
The frame rails with the mounting tabs for the PCB are identical and if you're lucky the infamous plastic front bezel will be intact and the side panels will be present. The front panel will have holes for the specific plug-in, but it is easy to make a new aluminum backer plate and front panel.
-Mac
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Re: Grid Bias Adjustment on 475A
" unable to get a visible spot on screen at the +15 V intensity level as indicated in the service manual. I had to crank the intensity up nearly to maximum, and then the trim pot (R1375) for grid bias had to be cranked to one extreme to see anything on screen."
Having done so much tube type TV work that I went cross-eyed.. LOL.... I got burned repeatedly back in the day with similar problems, so dont feel bad, this is normal...
1. Z-Axis is intensity modulation, which jives with lack of such related to "cant see anything on the screen". Thats on top of the regular CATHODE bias. Theres regular intensity, then on top of it, Z axis modulation OF that intensity.
The basic intensity must be correct first.
2. With all due respect, theres a lot of wild and frustruating guessing going on. The answer is never 'lift components and make measurments in good circuits"
Circuit analysis is required.
3. Bad Z axis amp. WHich transistor?, theres 7 of them. If its not being driven in Z axis modulation, that circuit might not be relevant. It doesnt take Z axis drive to put a spot on the screen.
4. The bad amp may not be related to the dim CRT. Very complex circuits here. I cant tell you how many times Ive chased the wrong problem!
5. Possibly the main point, there is **** NO such thing as grid bias.**** No such thing as base bias in transistors either. Control is exerted from GRID to CATHODE. A grid cannot control the space by itself. It is an electro-static couple with the Cathode! Base bias is meaningless without the emitter.
MUST measure the CATHODE potential.
The Cathode is NOT GROUNDED, therefore, its potential works with, or against., the G1 bias.
Further, these are not just DC bias circuits, they are pulse driven from T1320. The CRT Cathode receives pulses from T1320, thats not a filtered DC line thru CR1321.
There is a sensing feedback from the CRT cathode back to Q1306 probably to control intensity,
that circuit should control the SMPS associated with T1320. That transformer generates K, G and Focus potentials.
6. In tubes, the voltages on the elements between G1 and A can have a major effect on K-P current. Not as much, depending on voltage, typically as the G1, since G1 is closest to K,
but G2 can have a major effect. That CRT has FOUR GRIDS and all 4 and the Cathode MUST have proper voltages:
G1 control grid
G2 ~ 50V fixed bias
G3- Focus, ~ 2Kv
G4- Astigmatism, ~ 20-100V?
ALL of them have an effect on anode current, thus, brightness..
7. Low anode voltage can cause loss of brightness. That takes a HV probe.
Ignore the Z axis circuit, yes, I know thats what was "blown up" but troubleshooting MUST begin with verifying all the correct CRT voltages including pulses.
Not an easy problem to tackle.
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Re: Grid Bias Adjustment on 475A
On Sat, Jan 2, 2021 at 02:32 AM, Jeff Dutky wrote:
VR1374 is not shorted (I didn't check that it's breakdown voltage was 82 V, as
I sadly have no way to do that).
Jeff, Can you measure the voltage drop across the diode? That is partially how I discovered the "bad" VR1374 on my 475. You should measure 82V across the diode. Here is my conversation with Chuck Harris regarding the problem: ME: I must admit, I do not fully understand the DC Restorer. I have been reading these and other posts on the subject. CHUCK: Have you checked that VR1374 has 82V across it? That 82V puts the grid bias control into the range where the grid is in the cutoff region for the CRT. ME: YES! Testing across VR1374 I get about 66VDC. This seems at odds with your statement quoted above. This is with the + lead on the band side and the - lead on the opposite end of the diode. Reversing the leads gives a negative voltage of similar potential. So I have "Low" voltage and something like you are describing below, correct? CHUCK: High voltage zener's and the capacitors that parallel them often start to break down at too low of a voltage... they become leaky... and that would put your CRT grid into the blindingly bright range. ME: I was expecting 82Volts but perhaps I am not measuring this correctly? From your statement, 60-66VDC would put me in the "blindingly bright range", correct? ME: CR1373 and VR1374 check "good" with a conventional diode check, using a DVM. Both show infinity one direction and .576 VDC in the other. Like I stated previously, the scope works OK for the first 15-20 cold minutes of operation. After that it all goes nuts." END OF QUOTED CONVERSATION. MORE FROM SAME THREAD (after testing): ME: "I may have answered my own question. After writing that post, I thought that I might actually be following or understanding Chuck's explanation and that I might have a bad 82V Zener or a bad capacitor. Since I had a parts scope (the one that the CRT came from) I went out and pulled C1373 and VR1374 from that unit and installed them into my "malfunctional" unit. I am testing now, but the issue seems to be resolved. In addition, I put the unknown or "Bad" VR1374 into my Type576 and 577 curve tracers. In both cases, the component would show a normal Zener curve, then suddenly break down into a crazy looking curve (looked almost like a tunnel diode curve). Not sure what was going on, however, both the 576 and 577 showed the same results." END OF QUOTED CONVERSATION This scenario above may or may not be relevant. But if a "Low" voltage (less than 82V) is "blindingly bright", then does it not make sense that "High" voltage (more than 82V) would cause the display to dim? I can be way wrong, but you see my line of thinking? Good luck! -- Michael Lynch Dardanelle, AR
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Can't help you with data on those GE transistors but WB Parts seems to
have has a pile of them in stock:
Why bother trying to find unobtainum parts when Tektronix specifies "official" modern/current production substitutes (see crossref document)?
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Can't help you with data on those GE transistors but WB Parts seems to have has a pile of them in stock:
They were used by the military and exist under several different nomenclatures.
From my experience, the GE "pink" transistors were not particularly stellar performers, having fairly low gain and only moderate bandwidth. They may have been a high reliability part but that's about all I would speculate as being good about them.
In lieu of obtaining an original part, if unavailable, consider the following procedure.
I've never replaced one of those GE transistors with a like part (and never had to look back), originally preferring to select a suitable RCA device, back when they were still available. Today I would probably use a transistor by ON Semi/Fairchild or perhaps TI, again, selecting one to match parameters required by circuit.
I don't have an SC-502 to probe and the manual does not provide any waveforms, so I'm shooting from the hip here:
Q855 appears to be the transformer drive transistor in the DC-DC converter that provides most of the internal operating supply voltages. With an input voltage of about 33Vdc and a .3A fuse inline, Q855 does not have to be a very robust part. The 470pf C-B capacitor tells us circuit bandwidth demand is also not terribly high. I might try an On Semi fabbed TIP41, not for its power capacity but because it has the least gain found in that package/device category, perhaps being in the same realm as the GE part. For more gain in an otherwise also over specified part, the On Semi TIP 31C might be a good option.
Beyond this, someone else with experience troubleshooting an SC-502 might have more/better information to offer.
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.
toggle quoted message
Show quoted text
On 1/2/21 6:46 AM, Giovanni Carboni wrote: GE X44HR242
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Hi Giovani,
Look for the Tektronix part number in the service manual, it should be something like 151-0426-00.
Then use the semiconductor cross reference (big PDF file):
And it is indeed D44H11 as already said.
What's great with Tektronix is that they use mostly still available/made components.
Best regards,
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font/typeface for Tektronix binder spines - was Re: [TekScopes] Push button font
On 2020-12-14 9:04 a.m., toby@... wrote: On 2020-12-14 12:17 a.m., Chuck Harris wrote:
I'm pretty sure it is something put together
by Tektronix's graphics department.
Yes, and I don't think it's consistent either; after all, it spanned
several decades. It would probably be possible to find a suitable free
bold, compressed font that resembles it.
Turns out I have considered something suitable for binder spines before: View/Reply Online (#146250): /g/TekScopes/message/146250I also took a shot of my own shelf with some sample setting: /g/TekScopes/album?id=258709Of course Fjalla isn't the _same_ font as any of the binders, but the binders aren't consistent either, so it might help someone get close to the original look. You could also try horizontal scaling as desired (I couldn't do that in GIMP?!) --Toby --Toby
-Chuck Harris
snapdiode via groups.io wrote:
Cough, cough... Can someone perhaps identify the font(s) used on the plastic CombBind spines of the manuals?
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From Tek specs, it's a D44H11 NPN, currently available from STMicroelectronics, OnSemi, etc. at price of approx. 90 eurocents each
Icmax = 10 A
Bvceo = 80V
hFE 60 @ Ic = 2 A
Vcesat = 1 V
ft min = 50 MHz
Cheers,
Max
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11801C T2325 error diagnostic repair
Can anyone shed light on what is involved in repairing a unit showing that error?
Thanks,
Reg
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Michael W. Lynch
Kevin