FET Audio | Hi-End Audio & Electronics

June 28, 2021

hp 3324A functional generator service and repair

Filed under: Test Equipment — Spencer @ 12:04 am

The equipment also have RIFA cap and thus cleaning and service is needed.

Some inside photos.
Changed all 3 RIFA capacitors as they have body crack.
This set come with precision time base 10Mhz clock but the clock do not look very square wave in scope. Jitter is about 30ps, not the best in class.
The battery inside still above 3.2V after >25 years.
After assembly back, found the output amplitude is not able to set within 1 to 10V, thus there is an issue with the amplifier section which need further trouble shoot! Frequency setting is fine.
The problem on this sig gen was identified as the power switch one side open circuit at power ON position. Fixing the power switch and the signal gen is back to normal.

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June 27, 2021

Repair Panasonic Rick cooker

Filed under: Others — Spencer @ 11:52 pm

The cooler serve me about 10 years and start to give me some issue like timing set but auto cut off or some intermittent issue.

Open up and see the bottom very dirty and sticky and need full cleaning to remove all the dirty.
The pcb is very dirty and a lot of flux, thus clean with IPA to remove the excess flux.
There are two 10u 400V capacitor on the pcb and this is NO brand type. Thus replaced them with Nichicon 6.8u 400V long life type even the original cap measure good.
I want to highlight that the clips used in this cooker has a lock spring in it, just press down and then the pin can easily pull out from the IEC socket!
Bottom 4 screw no need to remove. a) IEC socket need to remove by one screw and one cover. b) Top cover hinge remove with 1 screw and also a cover, pull out from bottom of cover. c) then under the cover use flat screw driver to pull up the top section at hinge side. No solder is required for all dis-assembly steps.

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hp 6632A service and add front connectors

Filed under: Test Equipment — Spencer @ 11:41 pm

This is a very old hp power supply with HPIB control capability. It is 20V and 5A max. There is a fan to cool the set and thus it is a bit noisy when using this supply. Here is the work done to service it:

There is lots of dirty stick on the fan and thus cleaning is a must. Also remove the pcb assembly and all item from the case to do 100% cleaning the IPA.
Oh RIFA again and crack on surface, so leaking a bit is the norm!
Added front supply connector with sink in type banana socket. Do not want it to extend out as the front panel is also nothing much protruding from the surface.
No calibration is required as it is still quite accurate.

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June 24, 2021

Tektronix 1103 probe power supply

Filed under: Test Equipment — Spencer @ 4:39 pm

This is a very useful power supply and still selling a good price as Tektronix had made many good probes for use. Example P6247 and ADA400A etc. With this supply, the old probes can be used in modern oscilloscopes. I open up my set and check if there is any RIFA capacitor inside to cause trouble. Luckily there is non as the supplier use a EI transformer. The regulator ICs are just normal type LM317 and LM337 TO-220 type. I see my set was replaced one of them with lots of flux near the diodes! E-cap looks good shape and brand, no need any replacement!

P6247 1GHz probe which is good for measuring jitter on any circuit with differential input mode.
ADA400A is very good for very low level signal even for Biotech usage with extreme high input impedance. It has 0.1, x1, x10 & x100 times and thus 1mV / DIV will become 10uV / DIV in the scope! Also differential design and very good CMRR ratings but limited to 1Mhz bandwidth only. You know what, today Tektronix is still selling this probe!!!

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Tektronix AM503 current Probe amplifier & A6302 current probe service and TM501 Power supply.

Filed under: Test Equipment — Spencer @ 4:20 pm

Tek AM503 is the oldest current probe amplifier and there is no LED display on the range. Mine have the PCB corrosion as in the photo. Thus I use Methanol to clean the pcb but after that it is still do not looks very clean! Anyway there are few items need to be restored.

Note that all the old E-capacitors after checking is still working fine, no replacement !
One light bulb is not working, the one always ON! I changed them to LEDs but after that the resistors to limit current need to add in a 1.2k resistors. Note that the light bulb is driven by Negative voltage and thus I need to re-install the polarity of LEDs! I also reverse the two wire position and thus I need to reverse the plug on the pcb to get the right light on the current switch.
The Rotation current selection switch is a long switch covered. It has gold fingers to press on the gold plated PCBs at many locations for top and bottom side. The contacts are in pairs and either touch top or bottom side. To sort or to go through the attenuator resistors which is seated at bottom side. Since I have wash the pcb, I need to take out all the attenuator resistors to clean them one by one! There is lots of gold on this pcb and resistors or transistors!
The last thing I do not like the design of regulator of this instrument is that there are two power transistors located at the power supply unit bottom chassis for heat sinking. The connection is through the long gold fingers slots which sometimes may give to contact issue and make the power regulator not functioning well. Thus care must be taken when plug in the module into the power supply TM501.
Nothing wrong with the A6302 after disassembly for cleaning. Care must be taken to put back the ground contact springs and do not loss the metal bead. The current transformer is also be handle carefully.