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Tektronix 545B (V)
JOSE V. GAVILA (EB5AGV/EC5AAU)
Hello!
First than anything else, thanks to everybody who has suggested ways to deal with this repair. But saga continues... What seemed to be a simple trouble (power supply ripple) is still unresolved. Summing up, my 545B shows a distorted signal, obviously LINE frequency related, as shown in this oscillogram: Problem has been traced to the +350VDC supply, which has, under load, a large ripple (before the main relay actuates, ripple is lots lower). This oscillogram (sorry for the bad focusing of my picture) shows the AC voltage just after the rectifying diodes of the 350VDC supply (so it is NOT the regulated voltage): (LINE frequency in Spain is 50Hz) Please, note that it shows 500mV but I used a 10x probe, so each division is 5V. So ripple is high, about 18Vpp. As after this stage comes the series regulator (6080), driven by the voltage comparator (6AU6), I don't know if this ripple can be considered 'normal'... I have done similar checkings to other supplies in the 545B and none shows as much ripple under load. I have replaced rectifiers but trouble persists. I have also checked most of the 6AU6 surrounding components and all are fine. Both tubes have been swapped with good ones but problem remains. Could the transformer be bad and unable to supply the necessary current under load?. Could the +350VDC supply have a larger than usual load in the circuit, causing that drop? BTW, I feel like following somebody else in this repair; first, I have found that the wire coming from the power transformer for that supply was evidently resoldered... and, in fact, it was a cold soldering job!. Then I have found that the main fuse, along its holder, is just missing (I will replace it ASAP). Also, some diodes and resistors in the power supply section have been replaced. So I am afraid somebody tried to repair the scope and found that the power transformer was bad and discarded the scope... hope I am not right! Please, let me know what else could I check or any other info you can provide. Thanks! JOSE ---------------------------------------------------------------------- 73 EB5AGV / EC5AAU - JOSE V. GAVILA La Canyada - Valencia (SPAIN) EB5AGV Vintage Radio Site: European Boatanchors List: |
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Re: 2235/2215 info
Jeff Kershaw
Peter,
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I would appreciate your effort on this one. I have searched the world (online) to find out what it looks like. I don't know if you are aware or not, but the tube for the 2213A and the 2215A are the same as the 2235. I have installed without too much bandwidth loss (good to about 90 mhz) a 2215 tube in my 2235. Don't know if that would suit your needs or not. There are an awful lot of 2215s on ebay. With the cost of a tube (if you can find one) I think that $150 is an ok price for a used 2215. I just got one for $ 86. Good luck! Jeff KJ6FD -----Original Message-----
From: Peter Florance [mailto:audserv@...] Sent: Tuesday, August 21, 2001 5:47 PM To: TekScopes@... Subject: RE: [TekScopes] 2235/2215 info If my 2235M plate will fit on my scanner, I'll be happy to do it. It's still off as I'm still trying to get a tube for it. Let me know if you still need it. Peter Florance Audio Services 544 Central Drive Suite 101 Virginia Beach, VA 23454 757.498.8277 757.498.9554 Fax Email: mailto:audserv@... > -----Original Message----- > From: kj6fd@... [mailto:kj6fd@...] > Sent: Tuesday, August 21, 2001 8:35 PM > To: TekScopes@... > Subject: [TekScopes] 2235/2215 info > > > Hi all, > > I have a 2235 and a 2215. I purchased two accessory pouches that > (unknown to me when I ordered them) came without the "plate" that > attaches them to the scope. If someone has one of these and could > send a pic or scanned drawing of the plate so that I could fabricate > a couple that would be great! I have also unsuccessfuly bid on > several early 80's catalogs so that I could see what my scopes looked > like in the catalog. The catalogs went for over $30 and that was a > little rich for my blood. Perhaps someone has one that they could > scan and email? > > Thanks in advance for any help. > > Jeff KJ6FD > > > > To unsubscribe from this group, send an email to: > TekScopes-unsubscribe@... > > > > Your use of Yahoo! Groups is subject to > > Yahoo! Groups Sponsor ADVERTISEMENT To unsubscribe from this group, send an email to: TekScopes-unsubscribe@... Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service. |
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Re: 2235/2215 info
If my 2235M plate will fit on my scanner, I'll be happy to do it.
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It's still off as I'm still trying to get a tube for it. Let me know if you still need it. Peter Florance Audio Services 544 Central Drive Suite 101 Virginia Beach, VA 23454 757.498.8277 757.498.9554 Fax Email: mailto:audserv@... -----Original Message----- |
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2235/2215 info
Hi all,
I have a 2235 and a 2215. I purchased two accessory pouches that (unknown to me when I ordered them) came without the "plate" that attaches them to the scope. If someone has one of these and could send a pic or scanned drawing of the plate so that I could fabricate a couple that would be great! I have also unsuccessfuly bid on several early 80's catalogs so that I could see what my scopes looked like in the catalog. The catalogs went for over $30 and that was a little rich for my blood. Perhaps someone has one that they could scan and email? Thanks in advance for any help. Jeff KJ6FD |
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Re: Tektronix 545B (IV)
Stan or Patricia Griffiths
Comments below:
JOSE V. GAVILA (EB5AGV/EC5AAU) wrote: So, armed with the manual, I have been looking again at the power supply...Yes, I think you are on the right track. But I have not yet been able toThere are TWO electrolytics to check here: C679C and CC730. Did you check them both? Also, the 6AU6 comparator is goodIt could be a bad diode. If it were shorted it would blow fuses so if it is bad it must be open. If it were open, the ripple you see on the power supply would be at line frequency (probably 50 Hz in Spain) rather than two times line frequency like a nornal bridge rectifier would produce. About the 1A1 plug-in, it is of the 'old' type (6 nuvistors on it). ItGood luck, Jose, Stan w7ni@... |
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Re: Tektronix 545B (IV)
From my recollection of working on the tube B+
supplies many years ago, another possible cause is an open or leaky decoupling capacitor on the grid of the comparator tubes (6AU6). Check to see if your scope has a very small value (.001-.1 uF) capacitor in the grid circuit across the grid input to ground. When these go bad, the power supplies become unstable. Jim Reese --- "JOSE V. GAVILA (EB5AGV/EC5AAU)" <eb5agv@...> wrote: Hello!---------------------------------------------------------------------- 73 EB5AGV / EC5AAU - JOSE V. GAVILA __________________________________________________ Do You Yahoo!? Make international calls for as low as $.04/minute with Yahoo! Messenger |
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Re: Tektronix 545B (IV)
John Rehwinkel
So, armed with the manual, I have been looking again at the powerDo you have another 'scope so you can see the waveshape of the ripple? Obvious things, asActually, the 6080 is the regulator pass element -- it's a low-mu dual triode. Also, the 6AU6 comparator is good (I have checked in both cases withHave you checked the sense resistors? Although they check fine on-circuit, I suspect one ofThat's possible -- you can check these diodes with a multimeter, or look at the shape of the ripple. Ripple due to a bad diode causing regulator dropout gives a waveform from a pulse train (60 or 120 cycles) to a clipped rounded sawtooth sort of thing. Ordinary ripple is usually a sine wave or the scalloped wave of fullwave rectification. Generally I trace the ripple back from the output of the supply through the feedback network to the error amplifier and pass element. Wherever you lose the ripple is generally near the real failure. -- hope that helps, John Rehwinkel KG4L |
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Tektronix 545B (IV)
JOSE V. GAVILA (EB5AGV/EC5AAU)
Hello!
After another small trip (why do women _love_ to travel so much???), I am again at home. And, just today, I have got an original 545B manual in the mail. Sometimes, eBay is great; I got it for just $8 + shipping. And it has taken only three days to arrive to Spain (it was dated 18th) So, armed with the manual, I have been looking again at the power supply... to find that, yes, there is a trouble. -150V is good, as is +100V and +225V (less than about 5mVpp ripple on them). BUT +350V and +500V show no less than about 20Vpp ripple!. As the +500V is based on the +350V supply, culprit should be on that last supply. But I have not yet been able to locate the ofending part. Obvious things, as the +350V electrolytic cap filter and the 6080 rectifier are fine. Also, the 6AU6 comparator is good (I have checked in both cases with good tubes). Although they check fine on-circuit, I suspect one of the solid state rectifier diodes just after the transformer winding could be bad so the power supply has not enough available current and voltage drops on the 'bad' semicycle... But I need to check this. Anyway, is there any idea from your side? About the 1A1 plug-in, it is of the 'old' type (6 nuvistors on it). It seems to work fine. Hope it keeps going, as the nuvistors are not cheap items ;-) Regards, JOSE ---------------------------------------------------------------------- 73 EB5AGV / EC5AAU - JOSE V. GAVILA La Canyada - Valencia (SPAIN) EB5AGV Vintage Radio Site: European Boatanchors List: |
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Re: Defective HT-Transformer
Stan or Patricia Griffiths
Hi Urs,
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There is a man in Florida who rewinds some Tek HV transformers. I don't know if he has ever rewound one for a 536 or not. Bill Schell, AA4AY 10102 Winder Trail Orlando, FL 32817 USA I think I have scrap 536 and the easiest thing would be for me to remove the HV transformer from it and ship it to you. You can have it for $10 plus shipping if you are interested. Let me know. Stan w7ni@... Urs Suter wrote: To all |
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Re: Need DC508 LED displays, help!
Michael Dunn
At 3:49 PM +0000 2001/8/15, walter2@... wrote:
tell what it is displaying. this was a nasty part from Litronix,Surely there must exist a reasonable sub today. Have you looked into the various suppliers (mostly far east these days)? If you don't have catalogs, get me the specs (I might have them somewhere too), and I'll see if I can find something. ----------------------------------------------------------------- Michael Dunn | Surround Sound Decoder & Stereo Enhancer Cantares | Self-Amplified Speakers, Test Equipment 74 George St. | Ambisonic Surround Sound CDs and Recording Waterloo, Ont. | (519) 744-9395 (fax: 744-7129) N2J 1K7 | mdunn@... Canada | ----------------------------------------------------------------- |
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Re: Defective HT-Transformer
Phil (VA3UX)
I haven't taken apart a Tek power transformer yet so I don't know how the windings are arranged or if potting is used. But IF the HV windings are on the outside (which is fairly typical), you might get lucky if the shorted turns are near the outer layers. Carefully remove the outer wrap(s) of insulation, trying to leave them intact for later re-installation. Inspect the outer winding layer for the shorted turns. If the problem is there, unwind turns until you get to the short and repair it. There are a few ways of doing this so if you get to this point, e-mail me for further details. Disassembly of the core might be required (it's not as bad as you think).
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If you don't want to bother with a repair of this sort, take the unit to a local transformer shop and tell them you want it rewound EXACTLY as it is - between-layer insulation included. Some motor repair shops are equipped to do this, some are not. From Stan's book, there is reference to fellow in Florida that rewinds Tek transformers : Bill Schell, AA4AY Orlando, FL (407)282-4289 Phil At 07:02 PM 8/19/2001 +0200, you wrote:
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Defective HT-Transformer
Urs Suter
To all
The HT-transformer T801 of my Tek 536 is broken down. It seems that there is a short between two turns of a winding. As the scope is otherwise in a fairly good condition, I would like to rescue it. Does somebody have any experience in rewinding HT-transformers? Thank you in advance for your hints Urs |
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Re: 7L14 YIG
Stan or Patricia Griffiths
Hi Mike,
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Have you tried Deane Kidd <dektyr@...> for a replacement YIG? Another place to try is <www.sphere.bc.ca> Stan w7ni@... Mike McCauley wrote: Hi All, |
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Re: yet more 465M musings, and the evil 434
However, I wouldn't fault Tek and the "rookies" too much on some of
these issues. Don't forget that the 7000-series and TTL grew up together, so they were working on the bottom of the learning curve. I have a feeling that Tek was pushing the specs and doing a lot of selecting and having to interface to logic other than TTL just to make use of a complex TTL function to save on a lot of circuitry. When you're building 200 and 500 MHz scopes with a new 10 MHz and 100 MHz TTL technology, you're having to make do sometimes. The 7D01 was stuck in that same problem slot. Here you have a little plug-in that you expect to run at high speed and the fastest logic you have available for that task is ECL, some of the most power- hungry stuff on the face of the earth. Logic chips have come a long way since then. At least Tek had the innovation to try to work with one of the more robust supplies in the mainframe and build an efficient switcher into the 7D01 to get their logic supply. When the 7K series was developed, I don't think that Tek had envisioned some of the things they ended up trying, such as logic analysis or digital storage. I banged heads just a few months ago with one guy who was ripping the TM500-series to pieces. I'll defent TM500 to the hilt. That was an even more innovative design than the 7K scopes and what a broad and functional product line that was! There were instruments in there that had no equal back then, and even still today (FG504, AA501, SG505, AM503 and the entire oscilloscope calibration constellation). Tek's portable Neonatal monitor was usually preferred over any other model in a hospital. Tek's television products were second to none (specifically the signal and test generators) although I think most TV stations deferred to other brands of monitors for whatever reason. Even today, Tek seems to have had the best color laser printers around. The business side of Tek may have gotten in their way. There were plenty of bone-headed moves that hurt -- like IDG insisting upon sticking with bistable storage and waiting too long to use semiconductor memory instead, losing their graphics market after establishing Plot 10 software as the graphics standard. Dean |
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Re: 7L14 YIG
John Miles
Make sure your YIG is being biased properly, or it won't have any output.
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These things are usually rated around 20 MHz per mA of tuning current, and until you have 2 GHz worth of "current" flowing into the tuning coil (100 mA), they won't oscillate at all. Check to make sure you have 12-15V at the supply terminal and at least 100 mA of current flowing through the tuning coil before giving up. If the YIG is bad, you can probably substitute just about any 2-4 GHz YIG with little or no trouble. Most of them put out plenty of power to drive the mixer, and 2 GHz and 20 MHz/mA are very common parameters. The instrument can probably be recalibrated or modified to accommodate other tuning rates. -- jm ----- Original Message -----
From: Mike McCauley <mikem@...> To: <TekScopes@...> Sent: Thursday, August 16, 2001 6:45 PM Subject: [TekScopes] 7L14 YIG Hi All,problem.
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7L14 YIG
Mike McCauley
Hi All,
Ive got a used 7L14 Spectrum Analyser plugin with 1 remaining serious problem. The 1st local oscillator in that unit is a YIG (Yttrium Iron Garnet oscillator) that generates the 2-4GHz for the inital mixing. On my one it seems to have failed. My one seems not to be producing any output at all, and it looks like its been mucked around with (removed and replaced in a half-hearted fashion). The YIG module is a sealed steel can and appears not to be serviceable. It was originally made by Avantek. I havent been able to raise a replacement YIG here in Australia, and I dont really want to buy a whole new (second-hand) unit. Any ideas for sourcing a YIG or a faulty 7L14 with an OK YIG for reasonable money? Cheers |
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Re: More on my Tektronix 545B
Hi,
I followed this discussion for a while. I have a 1A1 manual series no. 20000 up with FETs in the input stages. The circuit between the CH1 input and CH1 output is only supplied by the -150V, +100V and +225V. I think the "bump" you see see is supposed to come from one of these 3 voltages. The -150V is the reference voltage for the whole scope and also for the other supply voltages. Its one of the first things you need to check and adjust during a calibration and once it is adjusted you must never touch it again, or you need to run your calibration again. The voltages are supplied through the following pins of the interconnecting plug: +225V pin11, -150V pin9, and the +100V runs through the filament of V252 and V261 in the timebase B and drives a current of about 150mA into pin15 of the interconnecting plug. This current flows through a voltage divider in the plug in. The voltage divider supplies +39, +11 and +5V to the plug in. The voltage at pin 15 is about 75V. If you need a scan of the 1A1 CH1 input circuit or the 545B power supply, let me know. I can do that on the weekend. By the way there is 545B manual on Ebay in Germany. I think its worth the try to see whether the seller ships it to Spain. If you can't get it shipped to Spain, let me know. Leo --- In TekScopes@y..., Stan or Patricia Griffiths <w7ni@e...> wrote: Hi Jose,should be able to find the test points for the power supplies on a ceramic strip onthe upper chassis toward the rear of the scope. The voltages will be markedon the chassis (-150, +100, +225, etc.) They should each be within 2% ofnominal and should have only about 5-10 mv of AC ripple on them. Thecalibrator and both sweep circuits should be off when checking ripple and you should beable to vary the line voltage + or - 10% of nominal and still have wellregulating power supplies. In the US, we consider nominal line voltage to be115VAC and vary it from 105 to 125 VAC while watching the ripple and voltageon each power supply with another scope. Both should remain stable.voltage from 210 to 250 VAC while watching the voltage and ripple on each of the5 power supplies (-150, +100, +225, +350, and +500 volts).compartment. This switch is found in the 547, 546, and 544 but not the 545B and543B. This means you MUST have a plugin installed in the 545B for the power suppliesto regulate properly.seen this many times. They just develop high contact resistance over time and youneed to replace it. There is nothing special about this switch except thatit should be rated for 10 amps.starting), if you had a manual, you would see that the heater voltage applied to thedelay relay (looks like a vacuum tube) is applied through a couple of normallyclosed contacts on the mechanical relay that eventually closes and allowsthe scope to function. If those contacts develop high resistance, the turn-ontime will vary irratically. You should carefully burnish all of the contactson the mechanical relay.as the scope warms up and their operation will change again when themechanical relay closes.supply problem in the 545B to me . . .put a should be apicture of it at: synchronizedcalibrator signal on Channel 1. as I havewith LINE, so it seems as a power supply filtering trouble. But have any hintno manual nor schematics, I can't work on this easily. Do you (or at leastfor this trouble?. Also, if somebody could scan the schematics ----the power supply section) of the 545B it would sure help a lot! 73 EB5AGV / EC5AAU - JOSE V. GAVILA
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Re: yet more 465M musings, and the evil 434
Miroslav Pokorni
We are all seating here praising Tektronix superior designs and at the same
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time listing lousy design practices. I think where we are going wrong is thinking of old tube scopes, which really were superior designs, and criticizing practices found in post 500 series. At this forum I hear of problems with various portables; at the present I own only 7000 series, so that is only family that I can say something about and that is not flattery, it is downright bad, especially when it comes to using digital components. I have seen things that rawest rookie would not do, like capacitive coupling to a clock of a counter without establishing DC level (found in S52), RC delay to plain TTL input using 680 Ohm resistor (in one of 7B plugs). All these things hobble along, but if IC is replaced with one from a different batch, as you would have in field or at the factory after few weeks, the circuit might not work. Even modules as shipped are operating with digital circuits robbed of its noise margin, not a goal of your designs for production, these are gentlemen amateurs playing at design. Personally, I did not notice 200 V electrolytic in 195 V circuit, but I did not work on power supply, yet. However, I noticed propensity for use of selected components, like selected 2N3904 for LED drivers. All these leaves an impression of design by rookies without adult supervision. Regards Miroslav Pokorni -----Original Message-----
From: walter2@... [mailto:walter2@...] Sent: Friday, August 10, 2001 9:20 AM To: TekScopes@... Subject: [TekScopes] yet more 465M musings, and the evil 434 One small thing to keep in mind, if your only experience with any scope is via the repair center, of COURSE they all seem broken. who sends in good ones to fix? The surplus ones showing up on ebay and elsewhere are all the ones that have been scrubbed for one reason or another, so it can be hard to see the good side of a product if you only ever see busted ones. Meanwhile, the 465M has no fan because for once, the power supply was correctly designed to dissipate the heat outside via the massive rear apron heatsink, what a concept! I hate fans in equipment, they blow dust and dirt everywhere, especially into the HV section, then fail. Tek seemed to have a real problem with heat management in most products, and there are many deflection transistors and Z axis transistors in the 7000 series that run far too hot, making the board eventually intermittent, or failing outright. we usually add some clip on heat sinks, and find life is greatly prolonged. two things always puzzled me about the generally superior Tek designs: if a part could be run to +100C, they did it, and if a supply was +195V, they used a 200VDC rating on the bypass cap. they could have used a bit of input from mil-derating tables, as these issues always came back to bite people over time. the 434: yes, this is an evil piece of hardware. the 1X / 10X panel lights for the vertical knob skirt (even after many mods) remain the worst piece of design in modern history. the scope virtually has to be disassembled to fix these lights, which burn out regularly. in the process, one is forced to notice all the other horrifying assembly problems. it works fine, it just better not ever fail, or all the available manpower in the western world has to be diverted to its repair for an extended period. I have to assume that people who liked Telequipment scopes liked the later Tek-inspred T900 series, not the earlier D series. I think the T900 stuff is great for low end work, and pretty rugged, they made their way into a lot of classrooms. The early Telequipment D series units are just frightening in every way. Still, people like what they are used to, so I suppose somebody must have bought those D-things in the Uk and fallen in love with them. all for now, walter ------------------------ Yahoo! Groups Sponsor To unsubscribe from this group, send an email to: TekScopes-unsubscribe@... Your use of Yahoo! Groups is subject to |
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