hp 6632A System DC Power Supply

November 15th, 2011

This is a very old machine used for automatic tester with HPIB control capability.  There is some very good old transistors as shown.  The transformer is still EI type and thus the set very heavy even the size is not big!  The bad thing about this supply is too noisy for lab use due to fan noise.  But it is a very low noise and high speed power supply from 0 to 20V and 5A maximum.  If you want to change the input AC voltage, you have to open the set and select by two switches near the IEC socket.

hp 3324A function generator photos

November 14th, 2011

I acquired this function generator in Oct 2011 and here is some internal photos to share.  My set is with the internal 10Mhz reference oscillator option.

Tektronix P6247 probe repair and internal photos

October 12th, 2011

I won this lot of 5 pcs Tektronix P6247 differential probes about 2 years ago from Seagate Singapore sales. 

1. Out of 5, only two probe tip heads are working and thus I am able to recover two probes in full working conditions after repairs and adjustments.  Thus it is a real bargain for me!

2. One box is with two burnt logic ICs inside and no way I can repair it!  What I can do is just repair the connection cable.

3. Another box is working but with X10 not functioning.  Guess there is some logic defective inside.

4. The other box is with unknown conditions as I have not tested it with a working probe tip head.  Believe it is working conditions as I check the voltage at probe tip socket is normal conditions.

5. All the 5 connection wires were repaired.  The usual defective point is the probe head joining point loose and control wires may be broken or intermittent connection.  I peel off more plastic of the coaxial cable ground and wrap it with some ground shielding cable and then solder the ground wire onto the frame of the tip socket end.  After that wire connection is checked one by one by multimeters.


This P6247 differential probe is very good for testing high frequency signal as it only has below 1pF capacitance value. It also has x1 and x10 selection, AC and DC mode plus the bandwith limit of 200Mhz.  I use that with a tek 1103 probe power supply and then I can connect it to any measurement equipment with 50 ohm termination like oscilloscope, frequency meter, spectrum analyzer etc…


Here I put up some photos which will be very easy to understand more about the repair:

FDA-1 PCM1794A DAC Clearance Sales – 50% off!

July 21st, 2011

* * * 50% OFF * * *

FDA-1 PCM1794A DAC clearance Sales and while stock last!

NEW prices in the STORE page.

I have updated a new user manual as below:

PCM1794A DAC Manual_r5

XMOS USB 2.0 Reference Design – USB 24bit/192k

June 23rd, 2011

I buy this XMOS USB 2.0 reference design evaluation board from Digikey for US$141.91.  It can receive USB 2.0 24bit/192k Fs signal and output to SPDIF optical and I2S besides stereo analogy input/output.  The board will require firmware programming before it can be used.  Details can be found in XMOS website.

Digikey item: 880-1017-ND



For I2S, the signal is labelled on the board  and I use 2.54mm pin header for connection to my PCM1794A DAC board.  The USB board use the power from USB connection at about 150mA and thus do not need any outside power supply.  The good thing about the reference design board is that XMOS provide all the details of design, schematic, pcb layout and software to make it work in almost any platform that can accept I2S or optical signal.


Since I use Windows system and thus I need to install a Thesycon drivers which is also free from XMOS website after registration. The diver works with the USB2.0 reference design boards without any issue but it will beep once every 30mins of use.  Overall it is a complete design and easy evaluation of the performance by both industry or DIYers.


Photo shows how I mount it piggyback on a daughter board and then plug into my DAC main board.