I seem to remember the service manual for one of the HP analysers on a web site -- I think it was one of the arcade game sites. Agilent may have a manual on their site too (they have a lot of old HP instrument manuals for download). The manual I saw incldued scheamtics. THere were a couple of PROMs (one was just the 7-segment decoder), but it was fairly obvious how it worked. The CRC polynomial is farily obviously critical. Did all signature analyser manufacturewrs use the same one? Hmm.. I am pretty sdure the display table was given in the manual, so you could work out the bit-level contents of the shift register. How easy it is gto go from that to the actual signal patttern is another matter... I never really saw the point of signature analysis. If you got the right signature then that signal was problaby correct, but if you got the wrong signature, OK, the signal was not doing the right things, but it doesn't really tell you _how_ it's malfunctioning. It strikes me as being a little better than boardswapping, but only a little. That saiid, if I could find an HP signature analyser at a low price I'd probably add one to the collection, but I doubt i'd use it much. -tony

I've seen HP service manuals that give signatures for various testpoint. They generally have a 'faultfinding' guide of the form 'If the signatature at pin 3 of U6 is not 23H7 then change U1, U8, U12, U24 in orde'. In otehr words they don't tell you exactly waht the fualt is and ovber half the time you'd have guessed it was likely to be one of those ICs (probably including the CPU, ROM and RAM) anyway I have a microprocessor-controlled HPIB extender for whaich the official manual gives signatures for various points. But there's also an undocumented (AFAIK) featuer to disable the CPU data buffer and force NOPs onto the data bus. That way you should get recognisable waveforms on the addres lines, chip sleects. etc. That's how I debug it. Some HP manauls are better htna others. In particular many of the computer nad desktop calculator manuals are pretty pointless. But since I've figured out how to fix some of those without any official technical info, I don't let the fact that they expect me to use a signature analyser to mean I have to use one :-) It's rare, alas, to get firmware listings in service manuals. A counterexample is the manaul for the 4-channel serial card in my P854, the manual for that has a commented source of the 8085 firmware. -tony

I see.... The is rumoured to have ebeen a program for th C64 that was supplied on floppy disk. The user guide included instructios for converting to cassette, the list of equipment required to do this included a C64 computer, a C2N cassette unit and a 1541 disk drive. However the service manual for my Tektronix 555 'scope does explain how to debug one half of the unit usign the other half (this is a ture double-beam ;'scome, apart from the CRT and low-votlage PSUs, it's almost 2 'sopes in one box, so you can use one to diagnost faults with the other). As would I.... I am otld there were inverse assemblers for my 1630, but I have no idea where you'd get them now. I think they were suppied on little tape cassetres to go in an HP82161 drive, I do have the drive...) Indeed, 0% of fautls are 'sillies' like bad swithc contacts ;-) But it's very useful to have the capability to find nasty faults for the reamin 10%.... I guess that's why I'd not use singature analusis much. In a commercial environment it may well find 90% of faults quickly and let you fix those units and get them back in the filed. Thing is, I generally only have one machine (fo a given type) to fix, and I have to fix that one, no matter waht the fault is. Odd... I was thinking of the pile of diagrms of machines from the HP9100B, via the 9800s and the 98x5s to the HP9000/200s -tony

Rew the Subject: line... To me '555' has only one other common meaning and that;s an 8 pin IC that can be used as an astable, monostable or bistable. I don't ahve a spare, I ahve the oen that came with my 'scope, and it's in use :-) I am pretty sure the conenctors were standard (full size Blue Ribbon ones). I dnn't know if they're still made, but you might fidn them second-hand sowmewhere. IIRC it's a straight-through cable, and it's jsut pwoer lines (include the AC feed to the heater transformer in the 'scope),. so the calgbe is not too critical. Ypu might be able to make one. -tony

It's problaby the nicest of the 500 series. I know I prefer it to the 556 a friend has, for example (even though the 556 has a higher bandwidth). It's a pity there never was a double-beam 'scope in the 580 seires. Now that would be serious fun. I thought EB91s (6AL5s, whatever) went on for ever... Anyway well done on getting another fine instrument going again. I have a 575, I never had the 175 add-on, so I am limited to 2A maximum collecotr current IIRC (!). I'd love a 570 (the valve curve tracer), but the 'real audip' brigade have sent pries of those sky-high.... -tony

Actually a storage version of the 555 would be fun. The only storage 'scope I know of in this series (and I don't have one) is the 549, which is a storage 545 IIRC. Incidentally, if you get a chance, l ook at hte 564 'scope manual, in particualr the storage system scheamtic. The cleaning lady mopping up the water put there by the flood gun is a classic... Eek.... One of the few times a vlave tester would have been reliable in finding the fault (see another thread). On the other hand, it's not hard to check the reisstnace between pins 3 and 4 with an ohmmeter. Years ago over here there was a simple battery + bulb continuity tester sold with varios valve sockets on it, The tester was wired to the heater pins of the sockets (pins 4 and 5 of the B9A, pins 3 and 4 of a B7G, and a segond B7G with 1 and 7 wires 'for battery valves only' and so on. It's actualyl quite useful for weeding out totally dead valves before you use the AVO Mk 4 or Tekky 570 ;-) -tony

On 1/28/12 1:16 AM, "Dave McGuire" <mcguire at neurotica.com> wrote: [snip] Congratulations! I have a 561A that makes me happy. :-) I do need to clean its switches, though. FWIW, I'd love to find a 3A74 plug-in for it. There's enough stuff that I do with vintage machines, requiring not screaming hot bandwidth but multiple inputs, that the 3A74 would just be far too cool for words. Just sayin'? I also have a HP 1741A that I use for faster things. At the Museum we have Tek digital 'phosphor' scopes. When people on this list say they don't own an oscilloscope, I wonder how they fetch water, cook their meals and eliminate their waste products. For folks who do what we do, a scope seems that basic, to my way of thinking. I don't use it every day, but when I need it there's no other tool that compares. -- Ian

On 1/31/12 8:28 PM, "Brent Hilpert" <hilpert at cs.ubc.ca> wrote: Have you ever heard the phrase "justifiable homicide"? OK, kidding - mostly. - Ian

Sometimes the scarcer Teks go for decent money - the very early gray cased scopes or the oddball 519 come to mind (but not 570 money). Some of the plugins do OK as well, like the polar plotting one, or the very difficult to find engine analysis one (sorry, I do not remember the numbers of these). But yes, the truth of the matter is that right now, the supply of classic Teks is far, far greater than the demand, and this is likely to be the case for the next 10 years. -- Will

Without wishing to re-ignite that particualr flame, I feel that some people associeted with said museum need to be LARTed. Now, When a donation is accepted by a museum (and of course the museum has the right to refuse any donaton), the donor should expect that the item will be preserved and not thrown out. Surely if the msueum doens't want somethign it owns, it should offer it to other museums, and failing that to collectors (such as this list), or sell it (if the donor hasn't specified that the item must not be sold) to raise money for the museum. No, a pricate collector may not conserve stuff in the same way a msueum should. But a skip (dumpster) won't conserve it at all. -tony

I have a tpye M (4 trace) for my 555. A 1A4 (4 trace, but higher bandwidth) would be fun, but I can manage with the tpye M. Once I had the Type M on one beam and a 1A1 in the other beam -- yes, 6 traces on the screen at once. For fater repetitive signals (like clock oscillators, the local oscillator in a 2m rig, etc) I use my 1S1, Yes I do have the probve for it (cathode follower probe with a small triode valve inside). It never fails to amaze me that there are plenty of programmers (even here) who don;t own a 'scope or logic analyser (or even a multimeter), but Iv'e yet to meet a hardware type who doens't own a C compiler and assmeblers and know how to use them. Actuallly, I use a logic analyser rather more than a 'scope. But I certain;y have several of the latter instruments... I am sometimes suprised by the fact that many people's toolkit is rather more limited than what I consider to be my 'portable toolkit' (screwdrivers, plilers, cutters, soldering iron, nutdrivers, hex keys, torx driers, etc). But then they probably wonder how I live without things that they would consider essential (like, sya, a guitar, or a bicycle, or a car, or sports equipment, or....) I guess we all have our own interests. -tony

Tony Duell wrote: The advantage of the signature analyzer (SA) was you can deal with circuits that have feedback loops more easilyand without the need to fully understand the operation of the circuit. For example servicing Atari Asteroid/Tempest/Battlezone vector generator (XY video games) there is a signature for each pin and thus you start at one end and work to the other of the schematic, where the signatures don't match you then have a likely suspect -slap on the logic comparator (Bugtrap or HP) or replace the chip. This often found the problem within a few minutes of setting up the tests. The primary saving was more lower level technicians could fix board that would previously have required far more training - and in a small service shop (or distributor repair facility) where you may only see that board once or twice a year it wasn't worth the time to learn all the workings to be able to fix it quickly. I use SA from time to time - it doesn't always help, but it is just one more tool on the shelf to get stuff fixed quickly... John :-#)# -- John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, VideoGames) www.flippers.com "Old pinballers never die, they just flip out"

On 01/24/2012 03:43 PM, Tony Duell wrote: I agree 100%. Last night I repaired an HP 5340A frequency counter and a Tek 7834 oscilloscope frame. (both glorious instruments) I had to trace through a fair amount of circuitry in both cases, and I learned a lot about both designs. In the "credit where credit is due" department, I had a kind assist on the 5340A from Dan Roganti who was here at the time. He kept telling me to look at the Range switch, and I kept saying it couldn't possibly be that switch contact making partial connection when it shouldn't have been...eventually I looked at it to shut him up, and sure enough, that was it! ;) It was holding the counter in reset. I now know how the control logic of the 5340A works. The 7834 frame had a 1M HV resistor on the focus power supply board that had failed open, putting a solid and uncontrollable 400V on the focusing grid. I now know how the focus power supply of the 7834 works...and what an amazing design the rest of it is. Holy cow, have you seen that scope?! In the case of the 3456A, though, it's an instrument from a working lab run by a friend of mine, and he lacks the budget to have it repaired, and I just want to get it working as quickly as possible to help my friend, by any method necessary. The alternative would be to loan him my beloved 3458A, but that beautiful instrument isn't leaving my sight! ;) -Dave -- Dave McGuire New Kensington, PA