2215A repair and restoration [Solved]
Today, finally, thanks to the slowest delivery ever!! in the history of the Spanish postal service, the CA3127E 's arrived :-)
Ordered 4th of March ( this year) delivery today June 1st, but.....
Drumroll.... NOS, slightly dirty pins, probably due to age, but they work!
I put the chip in a low profile 16 pin socket, that, with a piece of sellotape I attached to a long piece of shrinking tube.
With that I was able to move the chip-socket combo into the board's holes, underneath the attenuators, without the need of removing all of the input attenuators.
Long story short: the 2215A is back in business :-)
I am a happy bunny!
Will add pictures to the album.
I modified the title, and now it became a new thread, my bad, will try to remember not to do this again....
Pictures of the repair are here:
yes, the 2215A problem is solved... Again!
After I fixed the trigger issue it ran happily for about an hour, after that it went PHUFF!!
For no obvious reason the power supply went, like they often do in these scopes.
Again, by using the great document written by Hakan (Zenith), I was able to fix that quickly.
In my scope the CR907, Q9070, R909 Q908 and the fuse blew.
I replaced the parts as follows:
CR907 with a MUR460 (a bit tricky because of the thicker wires, but it's what I had)
Q908 was replaced by a 2N5401 (same pinout, higher voltage, same wattage)
Q9070 was replaced by a FQPF4N90C
R909 I replaced by a 4,7 Ohm resistor.
(in some schematics it was 33 Ohm, in others it was zero Ohm, and to avoid oscillation and still have a quicker charging of the input C of the FET, hence slightly steeper ON-Off switching, so less dissipation, I used 4,7 Ohm.)
The advantage I see in using a FQPF4N90C is, that it has a fully plastic case.
That allows for mounting it directly to the metal plate, instead of using the ceramic insulator Tektronix used.
I also added a TO-220 heatsink both around the FET as well as on the other side of the metal plate.
I put some heat conductive compound on both sides of the FET and both heatsinks to allow for better cooling.
And just because I can, I added a 12V fan to the scope by adding the following:
C965 4700uF 16V
R965 2,7 Ohm 1/4W
2-pin slotted connector
and a 60mm 12V DC fan.
The main PCB and housing are prepared for this, so it's an easy addition, and again,, some of the 22XX scopes do have this fan installed.
The fan runs at about 8-9 VDC, so it's really quiet, but it does add some airflow.
To restore the connection to the original thread here the link to my previous messages about fixing deflection and triggering in this 2215A before I changed the topic title....