Repairing can be fun. If you have a manual and schematics.
The schematics are all over the internet on ites like Bama, KO4BB, Kurts, eservice ect.
BUT, they have manuals of A-brands like HP, Keithley, Tektronix, Fluke ec. They allways had very good manuals including theory of operation, trouble shooting, schematics, board layouts, partlists ect. Service was very important. Agilent anfpd Tek still have pdf's from old equipment (like scopes from the 80's) Some manuals are over 100 pages. Tek even made books about repairing their gear in general.
But even from those brands it is hard to become manuals from rather new equipment .
A brand like Unit-T is only interested in low pice high volume. Not in service. And many Chinese brands have no problems violating patents so a publishing a schematic/manual is not always wise. I doubt if you will find a manual and schematics.
If you want to learn reparing, get some 60's-70's transistorised equipment from a known brand and allway first look for a manual. ( at this time in your "carreer" . When you know more, and know more people the risk of starting with rare instruments without a manual is sometimes worth a try.
And do not forget, if you are repairing instruments you most times need instruments that are a grade better then the one under repair.
Then the general rules;
1) check the powersupply rails on voltage and ripple
2) check the powersupply rails on voltage and ripple
3) check the powersupply rails on voltage and ripple
As long as they are not perfect you can not go on with other problems.
This sometimes even leads you to the main problem that is pullimg the line down.
Instruments needed for repair of instruments in general
Always:
- scope with 10X probe and 1X probe
- multimeter
For many repairs
- function generator and if you do RF a RF signal generator
- counter
- LCR meter
- ESR meter ( if you only have a simple LCR meter, with a really good one you can measure D, loss angle and/or ESR)
For multimeter repair also
- logic analyser ( if it is much digital stuff)
- standards ( volt, current, resistance)
For transmitters/receivers and RF gear a spectrum and network analyser comes in handy.
But do not let me scare you off, i started also with nothing ( 10 MHz scope and Fluke 77) and with some luck I most times still managed to get them going but the more gear I got, the more knowledge and experience the easier it became. But i started mainly with old tube equiped gear. That is rather bomb proof. If you cause a short or make a mistake most times no dammage occures. In this Unit T one slip of a probe can do much harm.
Home
Help
Search
Login
Register
