I think this is the right datasheet for the original:
The bipolar transistors optimized for switching power applications tend to have low gain and strong SOA characteristics. There should be plenty of other transistor types that will do - just try to get similar specs and SOA ratings. I think the -0426- was Tek's go-to part for lots of secondary side (low voltage) DC-DC converter use in that era.
Ed
|
Was Help with 2712 Spectrum Analyzer - Working now!
Hi everyone,
After a long time on the bench, finally my 2712 is alive and work 100%.
Using the suggestions that I received here, I start the service.
First I have made a visual inspection and look for some cable in wrong connector misplaced or lose but everything was ok.
Then I have checked all voltages and ripple on the power supply and all are OK.
The next step was to change the two batteries, an I would like to tell an interesting thing that happened when changing the battery that is on the GPIB board that powers the RTC.
I have the habit of always measuring the current drain of the batteries when I replace for a fresh one.
For my surprise, the meter shows 4mA.!! I thought it could be some capacitor leaking on the battery line or even some bad ICs.
Based on some previous experiences, I put the card back in the equipment and turned it on. As expected, the current drained from the battery was zero.
So I turned off the equipment and continued to look the current meter. It shows near zero for several hours.
This led me to conclude that when some ICs stay without power for a long time, when they are powered for the first time, they need to be initialized in some form to work properly and not drain this high current.
I removed the current meter and everything is OK with the RTC and battery for a few days.
Well, the 2712 still not work¡ So next I kept checking the 100MHz oscillator, as suggested by Paul / WB6GHK.
BINGO!!
There was no 100MHz. signal on any of the three output connectors and also on the output intended for the calibrator (with it ON of course).
So I removed the 100MHz PCB from the 2712 and removed the shields, which was a very boring job to do.
in the smaller shielded, I observed the existence of a kind of sponge in the position where the crystal is soldered, and that sponge was deteriorated, looking like a bubble gum and with the feeling of being damp.
As a result of this sponge being in contact with the crystal terminals, they oxidized a lot, and broke close to the crystal. Luckily I had a 100MHz crystal to put it there. It does not have the same type of packaging, but it fit perfectly inside the thermal chamber. So with everything still open I gave power on to see if the oscillator was working, and it was !! I checked all the outputs and found the correct levels according to the service manual.
As I can see, this oscillator has no adjustment, and I limited myself to measuring the frequency that was very close to the ideal.
After 15 minutes os warmup the oscillator was on 99,999.988 what I thought was reasonable and I set out to reassemble the shields and install the card in the 2712 to see the result.
After everything was in place, I crossed my fingers and gave power on the 2712 ¡
Fantastic! It is working!!
I followed the menu to proceed with the normalization, and everything was OK.
So to finish, I proceeded with the normalization of the TG which was also ok.
Now I have this fantastic instrument on my bench.
I would like to thank the friends who gave me advice to make the repair, and say that I am very happy to belong to this group. I hope that someday I can help someone too.
Happy New Year for everyone!
Marcus - PP5MS
|
Re: Grid Bias Adjustment on 475A
Michael Lynch wrote:
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
Yes, I measure 81.78 V across VR1374, which sounds like it's in spec (sadly, that would have been an easy replacement). All of this is making me think that the problem must further along the way to the CRT. I think that the grid being biased is pin 3 on the CRT, which is the acceleration grid immediately in front of the cathode. There are several components between the grid bias adjustment circuit and the grid in the CRT: C1371, CR1371, R1372, CR1377, CR1378, and R1379. Maybe I can get a better idea of what I should be seeing by reading the theory of operation section again. -- Jeff Dutky
|
Re: Peter Keller's Book Mailing Status
I am sure you in the US are aware and may have experienced this with mailing packages and letters for the holidays, but US mail has been considerably delayed, though it has gotten somewhat better in the last week. I had a media mail package shipped by an eBay seller and it took three weeks to get here. I would not be overly concerned if the US shipments seem to be taking longer than expected. Steve Horii On Sat, Jan 2, 2021 at 15:20 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
|
Re: A question from the unwashed relative to: I built a TM500 mainframe tester, and updated the design. Someone might find this useful?
A few things are missing from the descriptions.
1. There was a blank module available2. The modules could be user keyed for certain slots3. They could be interconnected unseen in the rear.4. There is/was a high power compartment (mentioned)5. Every module had their own separate power supply6. Uncommitted pass transistors were available for use.
It was a very nice system.? A one bay TM500 module could house a scope current probe for instance.
You could design your own test instrument with the various modules.
We made a laser scanner that mapped the output of a solar cell by position using two function generators, a power supply module, a multimeter and a glue module.? This drove a storage medical display scope from tek and mirror galvanometers.
The glue module selected x and Y modulation, it set the blanking level and x or xy scanning.? Anyway, the modules electronics were minimal.? All of the interconnections were behind the scenes.
Later, we were able to capture the data with a PDP-11 and A/D converters.? The display was then a VT100 with a board and CRT to turn it into a TEK display terminal.
The main purpose was to scan for defects and up the power of a laser to remove the defects.
The 5000 series added IEEE-488 to the mix.?
take a look here:
toggle quoted message
Show quoted text
On Saturday, January 2, 2021, 3:44:30 PM EST, Roy Thistle <roy.thistle@...> wrote: 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?
|
Re: I built a TM500 mainframe tester, and updated the design. Someone might find this useful?
I am also interested in a set of boards.
Bruce, KG6OJI
|
FAN to you, too, Giovanni!
I agree with Thomas that something rather generic, like the TIP31C that he mentioned, would probably work just fine. Even though it's an obsolete transistor, it still seems to be quite available.
I'm assuming you are in Italy (or at least somewhere in the EU), but if you are in the US, I could easily send you one.
-- Cheers,
Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
toggle quoted message
Show quoted text
On 1/2/2021 06:46, Giovanni Carboni wrote: HNY to everybody!
In my SC-502 scope transistor Q855 died. It is a GE X44HR242 in TO220 case,
but I was unable to get its specifications
in order to find a suitable substitute.
Thanks for your help
Giovanni
|
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.
|
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
|
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?
|
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."
|
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
|
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
|
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
|
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
|
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.
|
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
|
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.
|
ebrucehunter
Michael W. Lynch
Kevin