Search results

Search Forums New Posts
  1. S

    HP4274A

    It's not unheard of, but the ROM's going bad are unusual. If it helps, there are still a lot of 1970's/80's HP gear still up and running. They were built to last, and to be repaired when they don't. Good luck with the contemplation. I'll mention, did you check your power supply voltages to...
  2. S

    Tektronix 2235 troubleshooting.

    The only way to know for sure, is to desolder the switch, and THEN check it for continuity. My computer won't let me access your picture. Some pushbuttons are affected by the other push-button on-off configurations.
  3. S

    Tektronix 2235 troubleshooting.

    When you use the X-Y Mode, Q737 is biased 'on' to establish a HI on U760 pin 12, so that the A & B Sweeps are disconnected from the preamp outputs. When you're NOT using the X-Y mode, Q756 is biased 'on', and the X-Axis signal is shunted to ground. To USE the X-Y display, you're supposed to...
  4. S

    Variable AC Isolated Transformer (showing wrong voltage)

    I can't access the picture you sent of your variac. MOST variac's are 'unregulated', although some of the more expensive ones are. Yeah, basically a regulated variac has it's own circuitry internally to maintain a set voltage whatever the load applied. Most people USE a variac to get in the...
  5. S

    Tektronix 2235 troubleshooting.

    Watched your video. You're not sweeping. May be one of the trigger controls is bad, maybe a problem in the sweep circuit. I'd be looking at the trigger control manual switches first. As I said, the push-buttons are particularly suspect in a lot of the scopes I've worked on. I have assumed...
  6. S

    Variable AC Isolated Transformer (showing wrong voltage)

    I was thinking like Harald Kapp, the variac may be wired to read in a loaded condition. My second choice would be that the LED readout needs to be adjusted. Good to get the manual, and see what it says.
  7. S

    HP4274A

    I don't know if you gave up, or are still working this. I looked at the circuit. I'd be checking the A7 and A9 boards fiirst. I always physically pull the board and look for heat damage first. Sometimes the simplest things are the problem. I also wanted to say the test that's hanging you...
  8. S

    AWA DVD player not operating...

    The cap probably blew because one of your voltage regulators went out. You're in the right area (power supply), you just need to identify the part that failed that caused your cap to blow. A 22ufd at 450V will work just fine. From your readings, I'd be looking at the 5V regulator first...
  9. S

    Tektronix 2235 troubleshooting.

    I'd go with *steve*'s advice first. Assume one of your controls is locking your signal display out. Are you in a Triggered Sweep Mode? Do you have a bad probe cable installed right now? I've seen a lot of problems with the cheap push-buttons on Tektronix scope not working right, but if it...
  10. S

    HP4274A

    I don't have the file for the ROM. Almost half of the HP Test and Measurement instruments I work on were made in Germany. Did you try to find your U1 ROM? I know it's old, but some people still have some of the old HP IC's, and you might find somebody with a scrapped 4274A that you can get...
  11. S

    Inline connectors

    The price is normal for quality connectors that won't give you problems later. You can check for a single connector type that could handle all your circuits, but it'd probably be pricey. There are cheaper type Molex connectors that would do the job, but it sounds to me like you'll be...
  12. S

    Please identify this component

    You can find out what they are from the markings on the components.
  13. S

    Communications System Analyzer Parts - Urgent

    No, it was made by Motorola FOR General Dynamics. The "M" might mean it was made for military contracts. (Unless you're bveing funny about 'M"otorola) Most electronic components for it should be readily available once you get down to the circuit-level. If you mean you need specific...
  14. S

    Tektronix 2235 troubleshooting.

    My first advice is to get a manual for it, so you can follow the circuits. A lot of guys here say there are Tektronix-geared websites available on Google that will help also. We can reference circuits and give advice, but it'll be a lot easier if you've got a manual to know what we're...
  15. S

    Need a 3VAC Adaptor

    The diode/rectifier is to convert your 3VAC input to DC. You can't just plug in a DC adapter, because you've got the diode/rectifier circuit to contend with. If you're sure your NiCads are ok (which may be your problem), you can use a 3VAC adapter with a higher amperage than 100ma. The...
  16. S

    AC CAPACITOR FOR AC MOTOR CONNECTION

    Manufacturers color-code their own systems. What's the make and model of your garage door opener? It'll help a lot in identifying the wiring.
  17. S

    Inline connectors

    Then it sounds like your plan is the correct one. Each wire into the male connector (plug), and the same for the female-side (sockets). One thing to consider. You usually have an option of choosing a crimp-style for the pins and sockets, or a solder-cup connection for the wires to the pins...
  18. S

    Micro-switch

    Contact Element14 (Newark in the States, Farnell in the U.K.), and ask them. They would be able to contact Microswitch for your answer. (Or contact Microswitch yourself, and ask them). The DC voltage rating will be MUCH lower than it's AC rating.
  19. S

    Inline connectors

    Uh-oh. We'd need to see your circuit, to determine that. I assumed from your post, that you knew your circuit?
  20. S

    Communications System Analyzer Parts - Urgent

    Where are you at? It's easier finding old Motorola parts in the States than overseas. Did you Google the Analyzer and see what turns-up?
Top