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Add my 547 repair history
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# You can inject external H-signal to isolate sweep generator and H- AMP section. Set the scope to external H input and apply external H signal to verify the H-Amp is working. This will help you narrow down the problem between H-Amp and Sweep/Time Base. | # You can inject external H-signal to isolate sweep generator and H- AMP section. Set the scope to external H input and apply external H signal to verify the H-Amp is working. This will help you narrow down the problem between H-Amp and Sweep/Time Base. | ||
==David Wise's 547 Repair History== | |||
MY TEKTRONIX 547 OSCILLOSCOPE REPAIRS<br/> | |||
January 2021<br/> | |||
David Wise<br/> | |||
S/N 4369 | |||
Acquired around 2000 from Bob in South Bend WA<br/> | |||
Came with 1A4, 1A5, 1A7 #257 | |||
Had lossy epoxy HV transformer which failed. | |||
Rewound by Bill Schell. (Chuck Harris says Bill did layer wind on | |||
a spindle with #32 instead of universal wind with #38 like Tek, | |||
but mine looks like universal.) | |||
I still have 5642's, and the filament loops fit easily. | |||
MODS APPLIED | |||
Around 2000 | |||
M11722 (5680) Time Base 'A' Unblanking Circuit Resistor Added To Assure 'B' Trace Is Brighter Than 'A' Trace At Some Sweep Speeds<br/> | |||
* Add R377 1K, see manual page 163 'A' Sweep Generator<br/> | |||
* I also put a cap across it like Tek should have | |||
M11808 (5680) Horizontal Amplifier RC Network Added To Protect CRT Phosphor From Possible 'Turn-On-Flash' Burns | |||
* Cap yanks beam to side during power on | |||
* Add D561, C562, R562 | |||
M11809 (S/N 5830) to limit 6AU5 screen voltage to +125V. | |||
* Add D803, D804, R804 | |||
M12258 (S/N 6380) my field version: teepee a regular diode in series with D693 to prevent forward bias. | |||
PARTIAL | |||
M14194 (S/N 10730) Vertical Amplifier Components Changed to Improve 1-15kHz Frequency Response | |||
* They shortened the existing time constants and added a new long time constant | |||
* Part of the mod changes R1077 from 16K fixed to 30K variable. | |||
* I hand-selected a fixed resistor (24K) shunted across original R1077. | |||
* Did not do other parts: | |||
** Change C1077 value | |||
** Change R1126 value | |||
** Add R1091/C1091 | |||
M14860 (S/N 11270) Vertical Amplifier Diodes Added To Protect +100V Supply | |||
* Add D1114 in series with D1109 | |||
December 2017 | |||
SYMPTOM 201712: B Trigger: Auto works when Level is cranked one way but not the other. | |||
Effect reverses when you flip the Slope switch.<br/> | |||
CAUSE: D45 (B Trigger tunnel diode) Ip decreased from 10mA nominal to 6mA.<br/> | |||
I think that a turn-off transient from the Auto multivibrator was retriggering D45 which in turn retriggered the Auto multi and inhibited bright-line Auto.<br/> | |||
ACTION: Original part is 152-0154 i.e. TD253, which is Germanium. I replaced it with a GaAs Russian surplus 3I306L.<br/> | |||
FIXED. Seems fine even though the TD is slower(?) and has higher Vv and Vf. | |||
SYMPTOM 2021: HV transformer runaway!<br/> | |||
ACTION: Bake in instrument<br/> | |||
FIXED. Moisture ingress due to long sit in cold humid basement? | |||
SYMPTOM 20220520: Jitter in fast B sweep, triggering not as good as A<br/> | |||
I figure it's that Russian tunnel diode and I didn't notice before<br/> | |||
WILL NOT FIX | |||
SYMPTOM 20220520: Poor vertical HF response: -3dB at 35MHz not 50MHz; 10ns risetime<br/> | |||
CONTEXT: Using 8640B for f, 067-0521-01 for t<br/> | |||
ACTIONS:<br/> | |||
* Re-seat transistors, no effect | |||
* Re-seat plugin, some effect | |||
* Adjust per Table 5-8, some effect<br/> | |||
NOTE: L1157 has no effect, always slight wrinkles always in same spots<br/> | |||
NOTE: C1029 subtle effect but canceling bump also increases risetime slightly<br/> | |||
ACTION: Accidentally leaned on the delay line, DRASTIC EFFECT, flexed it, more effect.<br/> | |||
* Flexed it more, no further effect.<br/> | |||
* Now significant rolloff probably due to previous adjustment attempt.<br/> | |||
* But now able to flatten by adjusting Table 5-8 R's and C's.<br/> | |||
FIXED. 7ns risetime, 45MHz<br/> | |||
WHAT DID I DO?<br/> | |||
WATCH delay line, is it sick? | |||
SYMPTOM 20220520: Crumbling carry handle<br/> | |||
NOTE: Crumbling handles are on a 535A rail, probably 381-0204-00 (blue leatherette)<br/> | |||
I thought I had new ones but where are they?<br/> | |||
ACTION: Bought complete 381-0217-00 top rail with vinyl handles 367-0037-00 from eBay seller<br/> | |||
NOTE: 6" grip with captive square rings<br/> | |||
NOTE: Earlier 535A rails are 381-0121-00 (black leather) and 381-0149-00 (blue leather)<br/> | |||
NOTE: 547 handle also used on late 503 | |||
SYMPTOM 20220526: Flickering trace first few minutes after cold power-on<br/> | |||
CANNOT REPRODUCE 20220528<br/> | |||
HV Test Point<br/> | |||
* -1900V on Fluke 825A with Fluke 80K-40 (1000Meg), raster<br/> | |||
* -1898V on 067-0543-99 (100Meg), beam off<br/> | |||
INTENSITY string<br/> | |||
* -2015V on 067-0543-99, beam off | |||
TODO:<br/> | |||
M14928 (S/N 12110) Swap D672A-D for stronger, 1N4004/1N5060/1N5404.<br/> | |||
M15145 (11890) Resistor Changed To Ensure Operation Of Vertical Position Neon<br/> | |||
* R1187 was 330K CC now 301K 1%. I will simply select a carbon film part.<br/> | |||
M12876 (6300) Motor Base Changed To Improve Ground Connection<br/> | |||
* Just make sure we have a solid equipment ground<br/> | |||
MAYBE:<br/> | |||
M11122 (S/N 4750) Vertical Amplifier Gain Potentiometer Range Increased<br/> | |||
M11707 (S/N 5680) Vertical Amplifier Output Transistors Changed To Reduce Failures<br/> | |||
* Look for 153-0548-00 | |||
M12460 (S/N 6730) Vertical Amplifier Input Tube And DC Balance Potentiometer Replaced To Improve Vertical Amplifier Balance<br/> | |||
M14194 (S/N 10730) Vertical Amplifier Components Changed To Improve 1-15kHz Frequency Response<br/> | |||
M13839 (8420) 'B' Sweep Chassis Wire Modification Incorporated To Eliminate Sweep Free-Running<br/> | |||
* Wire strap to Q44.C relocated, and C44/C45 leads shortened | |||
WILL NOT DO:<br/> | |||
M12027 (6740) 040-0549-00 Trigger Circuits Rewired To Improve Stability<br/> | |||
M14339/M15344 050-0479-01 Disconnect Diode Replacement<br/> | |||
* 1972 | |||
* There's a mystery here. New Q286 is 151-0277-00. Manual says RCA 38520 and there's NO info on the web. | |||
* Common Design 1982 says 151-0277-00 is 2N3933 830MHz TO-72 Do Not Use. | |||
* NJSemi 2N3933 datasheet says 0.55pF, VHF/UHF amplifier. | |||
* 7L5 military manual TM11-6625-2759-14&P says 151-0230-00 is RCA 38520 but Common Design says it's 2SC1260 1GHz 0.7pF | |||
* New D286 152-0185-00 "replaceable by 1N4152" | |||
* Common Design says Do Not Use, use 151-0141-02 | |||
* New D291 is 152-0165-00, Common Design says 1N3579, 10pA at 3V, no info on web. | |||
* 556 Lecture Notes says it's a selected 1N3579. | |||
* D291 protects D286 from excessive reverse voltage | |||
* D90 (same as D291) added S/N 3130 M10510 "to protect disconnect diode". | |||
* D86/D286 were originally Tek-made GaAs and needed protection. | |||
* RA1092, no info except small-signal diode | |||
* Made by Microsemi and Freescale. It seems to me that maybe a 1N4152 doesn't need protection. | |||
M12463 (11890) Tunnel Diodes Replaced To Increase Power Rating | |||
* D45/D245 was 152-0154-00 now 152-0140-01 | |||
* D45 already replaced with Russian 3I306L | |||
M13384 (7960) Sweep Trigger Generator Amplifier Tubes Changed To Checked/Aged/Balanced Tubes<br/> | |||
050-0479-01 (12480) Disconnect Diode Replacement<br/> | |||
M11266 (5310) [timing caps drift due to temperature cycling]<br/> | |||
M11517 (5480) [timing resistors]<br/> | |||
M13653 (8290) [timing resistors]<br/> | |||
M14095 (10260) [timing resistors]<br/> | |||
050-0473-00 (12471) Sweep Steering Diodes<br/> | |||
M11212 (5130) [mag gain resistor]<br/> | |||
M12856 (10200) [calibrator resistors]<br/> | |||
M12130 (6730) [anti-slip feet]<br/> | |||
M11191 (8630) [standardize zener part numbers]<br/> | |||
M15322 (12800) [cabinet latches] | |||
[[Category:Instrument repair reports]] | [[Category:Instrument repair reports]] | ||