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Hi All, Could anyone tell me where I could find a "blank" vertical plug-in module for a Tek 555 series scope? Apparently there was a kit available at one time. Regards, Andrew

Greetings; I am trying to understand the failure mode of one of these in a 3A6. Both cathode tabs are melted and the 47^ screen resistor is smoked. With great trepidation, I replaced the defective tube after checking the asssociated 6DJ8s, xistors, and diodes. The replacement held and the screen resistor stayed cool. However, there is a DC imbalance on both traces that the controls won't comp. I suspected possible filament-cathode leakage in the otherwise fresh looking dead tube. No way to check for that now. I definitely don't want to risk a presently good 8233/E55L. Any ideas on the probable failure mode? Thanx in advance; Steve P.S., Hi Stan, nice to find you again. Great Resource!

Does anyone know where to get a decent front cover? I would like to take one to some of the plastic molding firms and see what it would cost to make up maybe 100 or so. This part seems to be the first casualty when the scope was new and now they want an arm and a leg for them. Maybe some one has already done this and can set me straight if the cost is too high? Thanks, Mike

Hello Thanks for the tips. I found a replacement cap from a 545A "hangar queen". Now the RM31a works great and no jitter. The cap in question was leaky, thus causing the ripple. Oh and the 475 motor is on it's way. I've been having email problems so I am slow to respond. Have a great day and may your fans run smoothly and your filters be clean. Windsor

morriso2002@... wrote: Hi Morris, There was an extensive modification to the 21A and 22A tunnel diode triggers at SN 11000. 21A and 22A timebases have the older tunnel diode trigger circuitry in them from SN 7000 to SN 10999. I would stay away from those unless they have had Mod Kit 040-0417-00 installed. The kit is very complex and includes a double sided circuit board and lots of hard to find parts so it would be almost impossible to try to put this kit together from scratch. The early TD triggers were very unstable and I can remember being very frustrated trying to get them adjusted so they would continue to operate reliably. They way to tell if the mod has been installed or not is too look in the timebase in question on the top of the chassis and just behind the front panel about an inch to see of the etched circuit board is installed there. The early 21A and 22A timebases had a couple of short rows of the small notch ceramic strips installed there with the early TD trigger circuits installed on them. Stan w7ni@...

Hi All, I am looking for a Vertical Amplifier IC for a Tektronix 2235A Oscilloscope. Tektronix Part Number is 234-0133-20 Can anybody help? Regards, Andrew

Hello, I have a RM31a that has a 54x CRT that works reasonably well. Thanks Dean :) There is a slight horz. jitter about 2mm worth. So I check the left deflection pin and see that there was no jitter. I check the right deflection pin and see jitter. So I go about measuring and changing tubes associated with the right deflection pin. Then I sleep on it for a while. It occured to me to check for jitter at very low sweep speeds. I connect my 7704a to the right deflection pin set the coupling to AC and volia I found that the jitter is 120 Hertz. So I measured the 500 V supply and found ripple of about 1 volt PP. So I added a small cap to help filter out the ripple and the jitter is gone! The moral of the story is that alway check the PS first! I fell in to the trap of seeing that everything else worked OK and assumed the PS was OK. Windsor

Hi All, I am looking for the following Tektronix parts: 317-0392-00 RES.,FXD,CMPSN:3.9K OHM,5%,0.125W 307-1020-00 ATTENUATOR,FXD:50 OHM,2X 307-1023-00 ATTENUATOR,FXD:50 OHM,5X 307-1024-00 ATTENUATOR,FXD:50 OHM,10X 1 of each would be great at this stage and if anyone has 2 of each I would like to know. Best Regards, Andrew

Hello! Well, after some time working with radio gear, now I am back to test equipment... Last time I powered my Tek 475, I found that the chopper circuit no longer worked. CH1 and CH2 work fine sepparately and also in ALT mode. But no in CHOP mode. So I guess it could be related with the oscillator in the chopper. Any hint?. I plan to work on it soon. Now I use the 485 or the 7603 to work. It is nice to have backup gear :-)! Regards, JOSE ---------------------------------------------------------------------- 73 EB5AGV / EC5AAU - JOSE V. GAVILA La Canyada - Valencia (SPAIN) EB5AGV Vintage Radio Site: http://www.geocities.com/eb5agv European Boatanchors List: http://groups.yahoo.com/group/euro_ba_swap

This is simply a 3900 ohm, 1/8 watt, 5% tolerance resistor. I expect a quarter watt unit would do fine. You can find these at Radio Shack. Or I can send you some. I have plenty (I bought out a Radio Shack when it was going out of business). http://www.vitriol.com/images/partswall.jpg You can actually make these -- though for compensated high frequency use, you generally have to parallel the resistors with small capacitors. There are two basic arrangements for resistive matched-impedance attenuators, "tee" style with two series resistors and one shunt, and "pi" style with one series resistor and two shunts. Here is an attempt at ASCII diagrams: tee attenuator: in o--/&#92;/&#92;/&#92;---+---/&#92;/&#92;/&#92;--o out series | series < shunt > | = (gnd) pi attenuator in o--+---/&#92;/&#92;/&#92;---+--o out | series | < shunt < shunt > > | | = (gnd) = (gnd) Note that these are unbalanced (signal referenced to ground) attenuators -- there are also balanced varieties. When I'm building these myself, I tend to use the tee variety, as it seems a little easier to wire up. Here are the resistor values for the listed attenuators (since the input and output impedances are the same (50 ohms), the attenuators are symmetrical, that is both the series resistors in the tee attenuator are the same and both the shunt resistors in the pi attenuator are also the same. tee attenuator: series (2) shunt 2X 8.58 141. 5X 19.1 55.9 10X 26.0 35.1 pi attenuator: shunt (2) series 2X 291. 17.7 5X 131. 44.7 10X 96.2 71.1 Resistor values are in ohms, and I've rounded them to 3 places. Note that most of these aren't standard values, so you'll have to obtain precision resistors (a good idea any to maintain calibration) or build them up out of combinations of standard values (this doesn't work well for high-frequency use). Good luck, John Rehwinkel spam@... (currently repairing a 7844 and a 570)

I'm not sure I'm on the same page here. What kind of plan? Which caps? Dean

Can anyone find the current rating of the 6.3V winding on transformer T402 (#120027) from a type 517 power supply ? T402 may actually be a dedicated 6.3V filament transformer since there were something like 106 six volt tubes in the 517. I don't have the thing in hand so I'm not sure. There should be a prize if someone can answer this. Thanks in advance. Phil

Hi, I am a student and I got my Tek 465B from an eBay auction. I know how to use the oscilloscopes, but have no experience in idendifying and fixing problems in oscilloscopes. The problem is that, the trace or a signal width is limited to maximum 3 divisions on the time scale (i.e. when the Horizontal Position knob is fully turned to left). Turning the Horizontal Position knob to right will reduce the width to 1 division on the time scale. I cannot get this to occupy the full with (10 divisions) on the screen. Is there a screwdriver adjustment knob somewhere to fix this or is this an internal problem? (Also I notice the trace travels from right to left, Is this normal?). Apprciate if someone can help me to identify the problem. Thanks - Shiran.

Hello! I am in need of some info about the 7S14 plug-in... is it worth $150 in operating condition?. How does it performs? Please, any information will be welcomed. Thanks! JOSE ---------------------------------------------------------------------- 73 EB5AGV / EC5AAU - JOSE V. GAVILA La Canyada - Valencia (SPAIN) EB5AGV Vintage Radio Site: http://www.geocities.com/eb5agv European Boatanchors List: http://groups.yahoo.com/group/euro_ba_swap

Just a note to those who may have some 12AX7s in their equipment (e.g., 549 has 2) or junk box: Check your stuff for Telefunken tubes. There are some strange people out there who pay big bucks for them (on eBay for example). Also, take a look at the tube's plates. If they're smooth (without any corrugations), they're even MORE valuable. I've recently seen (used) smooth ones go for U$25-30 each, and ridged ones for U$15-20 ea! NOS (unused) would presumably fetch even more. Altogether, I've found six smooth ones in my junk and 549! Replaced the 2 in the 549 with some *non*-valuable ax7s I had, and, big surprise, it works just as well ;-) p.s., I just sold mine for U$51, $68, and $123 a pair!!!!! I can only guess that the $123 pair went for so much because of the good condition of the labelling on it! Yet, the other two pairs went in inverse proportion to legend quality. Crazy audio nuts... ----------------------------------------------------------------- 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 | http://www.cantares.on.ca/ -----------------------------------------------------------------

Methinks the tops of my boots are needing a few more inches to clear the effluent which is building. Ain't no way the human sense of hearing has the bandwidth or the dynamic range that even modest test equipment has. There is not a doubt in my mind that I could write up a page of pure fiction (including some references to Atlantis and perturbences in the orbit of Io) and be able to sell my own homemade capacitors (I think that Saran wrap and aluminum foil will do nicely) and homemade speaker wire (I think that braiding some Solder Wick with spark plug wire may do the trick) and sell these items for fantastic amounts of money to Golden-Eared audio enthusiasts. Easily. It wouldn't be honest, but sometimes when I read all the ads, it appears that this crowd doesn't want honesty. Audio is so darned subjective that no one person can say what's right. More of my opinion (and that's exactly what it is) should be showing up in the October 2001 installment of "Q & A" in "Poptronics". I'll gladly put my 12AX7's on the block. Lessee, here's the ad copy: "Specially burned in for smooth audio quality without the sharp edges one experiences with all new tubes. The lettering on the glass has been removed to improve the transparency of the sound. Tubes with specially-rounded exhaust nipples available upon special order." Dean

Hello, Perhaps a change in subject is would be good right now. I caught up on the topics because I recently signed up. Anyway did you check the horizontal plates for jitter ? Because I had a problem just like yours with thick trace going up and down but laser sharp going across. See the thread: RM31a jitter adventure :) Windsor Chan _______________________________________________________ Get 100% FREE email for life from Excite Canada Visit http://mail.excite.ca

Hello, I'd agree with both Stan and Dean. If you want to meet the specs spelled out in the manual, then you should go by the manual. But I and many others the ballpark estimate is good enough. For the record I use a oscillator in a can from a scrap computer to check that the timebase is more or less where it should be. And if you need to be bang on use a counter. Windsor Chan _______________________________________________________ Get 100% FREE email for life from Excite Canada Visit http://mail.excite.ca

Interesting range of opinions thus far.. and *yes* there's a relationship to scopes in all of this, IMhO. At least re test equipment operation, there are physics-laws + state of the 'mensuration art' which together define what you may expect to "see" -- and how much of that CRT picture you "believe". (But even there! re risetime artifacts, delay-line aberrations and such: it is never a *perfect* representation: just "close".) As a Marantz, Crown, etc. mini-dealer in the '60s - early '70s, I imagine I've heard most of the philosophical arguments too: the physics (not so precise as an engineer-mentation wants to suppose) -- not so fuzzy as an artist might want to argue. (sigh) To me the final arbiter ever was: The AR (Acoustic Research) "Live VS Recorded" concerts in these times of great audio strides. Here the "listenien room" WAS the same exact site as the live performers inhabited. It was classical music; never mind one's taste: all the difficult instruments of the orchestra had to be re-produced! Musicians would play then secretly [cackle] switch to "pretend mode" as the speakers + electronics took the next passage. Bottom line: where no one (?) or a very few in audience could come close to IDing the transitions *correctly* -- THAT is "good enough". Period. Now about that chirping 485 I have to do the ESR- capacitor-dance over; it's a PITA to work on compared to a trusy 545B.. I don't have anymore :[ (There: scope related, for the CPAs and other Content Cops? clucking in the techno-correct peanut gallery.) Ashton - - a mime is a terrible thing to waste -

Hi there, This might be a bit offtopic since I'm bringing Telequipment scopes to discussion. But then again Telequipment was bought by Tektronix in the late 60's I think, so I hope all is well :-) As I said I own two Telequipment scopes (bought them for 30 pounds), models D43 and DM53A with the following problems: a)D43: Although I have both beams on the crt and the timebase seems to be working ok, I have neither focus nor any signal at all (ie just two thick straight beams); b)Lots of trigger misfires. The signal "wanders" across the crt window. Trigger level looks ok though. Timebase looks ok; Can you guys advise me on what to do or where to start? Both crt's look ok (no burnt spots, etc) - I'm sure we're talking about minor stuff here. Both scopes seem to be built like a tank - the quality of wiring is superb - and there's life in them - it would be a shame to scrap them just like that. Thanks in advance for all your comments/suggestions/tips Best Regards Fernando Fonseca Portsmouth, UK. ---------------------------------------- John Lennon's dead. Phil Collins alive?! ---------------------------------------- ____________________________________________________________ Do You Yahoo!? Get your free @yahoo.co.uk address at http://mail.yahoo.co.uk or your free @yahoo.ie address at http://mail.yahoo.ie