2755AP - 2nd LO tuning failure when span <= 500 Hz
Have had this 2755AP for 10+ years; for the first time in recollection I've needed to use very narrow span width (to inspect output of a HP synthesizer). Frequency being inspected is 1000 MHz. When span is set to 500 Hz/div, I get occasional "Tuning failure 2nd LO". When span is set to 200 Hz or 100 Hz/div, the error messages are more frequent but not continuous. The error message does not appear at power-up self-test.
I used Shift 0 3 to access "2ND LO DIAGNOSTIC AID".
Doesn't appear I can post the photo here, but this is the displayed info:
TUNE VOLTS NOMINAL=0.01V DAC SET = 0.19V
2ND LO FREQ DESIRED = 2.182.000GHZ COUNTED = 2.182.099GHZ
OFFSET FREQ DESIRED = 18.000 000MHZ COUNTED = 17.900MHZ
OFFSET SETTING ACCURACY 294.912KHZ
The verbiage in the service manual (volume 1, page 6-12, section titled "TUNING FAILURE - 2ND LO" includes the text
"The offset setting accuracy is the maximum permitted difference between the actual and desired offset frequencies. The setting process ends when the difference becomes less than or equal to this value. The tolerance depends on frequency span and band."
I'm puzzling over what this is trying to tell me.
Also I believe the analyzer has a built-in back-up battery which has not been touched in at least the 10 years I've had the unit here. Does the back-up battery store some calibration coefficients that could have been lost? There has been no error message related to back-up battery specifically.
Thanks!
Dave
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Re: SC504 high Voltage Board Potentiometer
Just a guess, but after some digging I suspect there is a different HV board layout/configuration for the 2 different CRT's available... anyone has any insight?
Regards,
Barry
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Re: SC504 high Voltage Board Potentiometer
I can't even tell what is the latest circuit configuration. Anyone have an idea?
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Re: Hello/Tek 547 issues.
One thing to check is whether one of the horizontal plate connections isn't, well, connected. They're easily pulled off, so take a look around the crt connections (not at the base, but where the plate terminals emerge from the side of the jug).
Hope you get lucky!
-- Cheers
Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
420 Via Palou Mall
Stanford University
Stanford, CA 94305-4070
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On 3/14/2025 12:09 AM, Diabolical Artificer via groups.io wrote: Hello, my names Andy AKA Diabolical Artificer. I build valve amps & interested in vintage tech as well as using a 545B daily as my main scope. I also have a 585A & currently trying to get a 547 working. I'm on a few forums as well as having a small Youtube channel where I post my doings.
I've been working on a 547 ser # 100091 for the last few weeks. after testing/re-forming all the big PSU caps I powered it up. After sorting some silly mistakes I'd made I checked all the PSU rails - all were in spec. However after the scope had been powered up for a few hours the EHT tfmr was found to suffer from the usual insulation breakdown. I replaced the EHT tfmr & replaced the valve diodes for silicon diodes.
I have a trace but it's not the full width of the CRT, it's "stuck" on the LHS. Suspected hor amp. I've done a lot of checking on the horizontal amp. I took DC voltage readings - noted a V reading on the OP of V584B cathode - +3.95v (should be 325v ish) I checked all the transistors (I'll call em Q's for short) in the scope as well as the diodes. I also checked the valves - all ok. Found some dead Q's - Q543 & Q554, replaced with 2N1893 & 2N4890. also found some dead diodes - D561 & a diode in TB B multi vibrator circuit. I used what I had, not the right Tek parts.
So, TB B is working, TB A not, I have limited X trace length also limited Y adjustment & no intensity adj. At the moment I'm concentrating on the X & Y OP circuitry then I'll move onto getting the TB's sorted. Any ideas where to look re X limited trace length?
Regards, Andy.
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Re: Salvage yard rescue: Tektronix TU-50. Some questions from a non-tech
I hope I can too, it’ll give me a reason to set up a dedicated 500 series calibration bench, something I’ve been meaning to do.
Right now I’m sitting on 17 1950’s/1960’s scopes.
556
R556
(2) 547
545
310A
585
(3) 532, one working
(4) 575 Mod 122C
565
561A
564B
(2) Type 130 LC meters
Engineering Power Supply
Type 180 Time Mark Generator
Plus a 7904 and a bunch of TM500/5000 stuff.
Had to list them out to count them!
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Hello, my names Andy AKA Diabolical Artificer. I build valve amps & interested in vintage tech as well as using a 545B daily as my main scope. I also have a 585A & currently trying to get a 547 working. I'm on a few forums as well as having a small Youtube channel where I post my doings.
I've been working on a 547 ser # 100091 for the last few weeks. after testing/re-forming all the big PSU caps I powered it up. After sorting some silly mistakes I'd made I checked all the PSU rails - all were in spec. However after the scope had been powered up for a few hours the EHT tfmr was found to suffer from the usual insulation breakdown. I replaced the EHT tfmr & replaced the valve diodes for silicon diodes.
I have a trace but it's not the full width of the CRT, it's "stuck" on the LHS. Suspected hor amp. I've done a lot of checking on the horizontal amp. I took DC voltage readings - noted a V reading on the OP of V584B cathode - +3.95v (should be 325v ish) I checked all the transistors (I'll call em Q's for short) in the scope as well as the diodes. I also checked the valves - all ok. Found some dead Q's - Q543 & Q554, replaced with 2N1893 & 2N4890. also found some dead diodes - D561 & a diode in TB B multi vibrator circuit. I used what I had, not the right Tek parts.
So, TB B is working, TB A not, I have limited X trace length also limited Y adjustment & no intensity adj. At the moment I'm concentrating on the X & Y OP circuitry then I'll move onto getting the TB's sorted. Any ideas where to look re X limited trace length?
Regards, Andy.
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SC504 high Voltage Board Potentiometer
Greetings!
I have an SC504 on the bench. What is the 250 ohm trimmer pot that is on the Hv Board? I can’t find any documentation on this mod.
Insight would be appreciated!
Barry
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The VERTICAL POSITIONING pot looks to have been completely, and very cleanly removed. The violet striped, red striped, and black orange brown striped wires that (I assume) went to the pot were cut pretty close to the DC BAL pot and neatly tucked away.
FWIW the s/n of this unit is 002835 and on the backside of the front faceplate is written RCA 3374.
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Re: Like to say hello and ask a question about my Tektronix 465 ocsilloscope
Hi, no I meant modifications on the 465. During the years of production problems in the field can occur and as result modifications to improve the performance and reliability, quality etc.
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Re: Tek 2236 Control Button Error
A tiny update...
The 2236 is successfully apart. I did find the CH1 probe sense problem, apparently TEK forgot to solder the W9100 connection on the A3 board, the wire was in the PC board hole, just unsoldered. Still investigating for other connection problems that might be the cause of the "Control Button Error" message.
As long as I am inside, I am going to replace the "Riga" filter caps, too.
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Re: Salvage yard rescue: Tektronix TU-50. Some questions from a non-tech
On Wed, Mar 12, 2025 at 10:15 AM, Ferrous Steinka wrote:
(The leveler) seems quite do-able, just a handful of resistors, a cap, and
a 6110.
True. But, it's not the same is it. Here you are... pretending... and fantasizing... about being back in the day... of vacuum tubes and zinc plating... when what you are holding in your hand isn't authentic; but it connected to something that is. I suppose... more dreaming... or more beer required. -- Roy Thistle
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Re: Salvage yard rescue: Tektronix TU-50. Some questions from a non-tech
On Wed, Mar 12, 2025 at 09:36 PM, Eric Boyle wrote:
I just hate to see these golden age of electronics jewels going to the scrap
and being destroyed.
Well... I hope you can get it. You'll have to find the head/probe... or construct it..not hard; but, tedious. IMO... it won't satisfy someone who is new/newer to electronics: even though it is a Tek made calibration unit... it doesn't come close to even reasonably cheap modern gear! ... it's big, heavy, power hungry, high voltage gear, with lots of tubes. (The kind of stuff we like... but the shine wears off quickly... if you're not one of us.) IME... for the non-bitten... it goes to holding down the basement floor, until the better half orders it to be ditched. So I hope you get it. -- Roy Thistle
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Just the knob or maybe a parts unit?
Thanks!
Marty
KL7AM
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On Thu, Mar 13, 2025 at 05:11 AM, Dale Drake wrote:
Looking for recommendation on a reasonable asking price.
at a flea market? doesn't make sense. -- Roy Thistle
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On Thu, Mar 13, 2025 at 10:26 AM, Stuart Cody wrote:
You’ll see what stuff actually sold for.
Only if you pay for Terapeak... Ebay's for pay, marketing tool, that shows what items actually sold for... which can be surprisingly less than what the listing indicates. otherwise it's just Ebay B.S. -- Roy Thistle
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151-0574-00 / WG1308 Substitute
Greetings,
What is the recommended substitute for the WG1306 diode?
120v 150ma trr=4ns
Barry
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For appraisals, my go-to is eBay completed items.
You’ll see what stuff actually sold for.
There have been no recent sales on the -D model, but a -C sold for $270. Seller was asking $300.
Put it on eBay at $325. Wait a month, reduce it then to $299.
The flea market will bring $100-200, if you have a buyer with strong interest. Not my first choice.
Via iPhone; cel is 617 283 8263
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Re: 492 has no 110 MHz IF
if I understand correctly (big if!), that intermediate frequency is produced by mixing the 2nd LO 2182 MHz output with the 2072 MHz input signal from the 1st converter. I'm trying to understand why the 110 MHz IF is dead, even though the LO signal is present at approximately the right level. Very small “if”, I’d say.” -;( You may look at those two ~2GHz signals with your 7T11/7S11, if you have a suitable sampling head, like e. g. an S2 or S4 and probing setup. Same for the 110MHz mixing result, if even to see if any of it is there. Not sure what Dave P. means about signal levels. Operating input level <= 1Vpp or 350mV RMS. Safe PP 5Vmax. Recommended input level between say 50mV RMS and a few 100mV RMS at most, ISTR. You’ll need a faster counter plug in than either a 7D14 or 7D15 to measure their frequency. Take the impedances of the signals you look at and your test setup into account but I guess you know all that. Raymond
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Re: Like to say hello and ask a question about my Tektronix 465 ocsilloscope
Did you mean 2467B? DaveD KC0WJN On Thu, Mar 13, 2025 at 10:57 Jean-Paul via groups.io <jonpaul= [email protected]> wrote: Rebonjour Wilfred
Bravo for the new 465.
Since the 1970s the successors were improved, so 465B has better control,
LED not incandescent etc.
Nowadays the last of the analog CRT scopes from Tektronix are great buys,
2465,2465B, 2475B, etc.
A 1990s scope has much better reliability than the 1970s you have.
Just my experience
Jon
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Re: Like to say hello and ask a question about my Tektronix 465 ocsilloscope
Ok, thanks.
Is there, given the serial number (109003), any indication that some modifications are already executed factory wise ?
I will have a check of course on the components both of you mentioned.
Wilfred
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Eric Boyle
Diabolical Artificer
rivet_head
Wilfred
Stuart Cody
Raymond Domp Frank