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MAINTAINING THE FEC200: Introduction


We believe it is in your best interest to service the FEC200 at the board level. However, complete documentation is provided so that you can service the boards at the component level if you wish. You should be aware that some of today’s circuit boards are complex. They require a high level of skill as well as a thorough understanding of the operation of the circuits involved. This caution does not apply to every board in the system however.

There are few of these particularly critical boards in the tester. These are identified later in this document. You may wish to purchase spares of these boards. We keep spares on hand for shipment on short notice. We can also repair almost any returned board quickly for return shipment the day after we receive it.


Almost, but there are some exceptions. The most important exception is the relay section. Although the B503 (B508 & B509 for FEC200) relay matrix board (s) can be removed and returned for service, most of the problems will be stuck reed relays. You should replace these reeds. There is a diagnostic routine in the software package to help you find a bad reed or to discover other problems with the relay boards. This diagnostic is self-documented. It is a good idea to become familiar with this routine before it is needed. You will find it labeled RELAYS under DIAGNOSTICS.

The DC power supplies also contain some components that are not on plug-in boards. Fortunately the supply voltages are easy to check and repairs to these supplies are fairly routine.


  1. +5v +/-15v This supply is located in the top chassis with test points on the front panel. The voltage tolerance is +/-5%. The regulators are the common 7805, 7815, and 76915 IC voltage regulators. A TIP34 power transistor is used to boost the output current of the 7805. These components are about the only ones likely to fail.
  2. +12V This supply operates the relay coils. The 12V regulator and booster transistor are located on a plug-in board in the top chassis. This also has a test point on the front panel.
  3. .+12V for Handler Interface Each B502 station interface board has a 7812 regulator for the 12V that is supplied to the interface. The raw power for these regulators is in a small package near the sockets for the 4 boards.
  4. RAW BIAS SUPPLY This supply in the bottom chassis is used only to supply forcing power to the DUT. The tester will go through the motions logically with this supply completely off, but of course will not supply power to the DUT.
  5. This supply has only three outputs supplying unregulated power. The 600V (nominal) output supplies operating power to the feedback amplifier on the B507 500V bias supply board. This board in turn supplies Reverse forcing and Forward forcing for ranges 4mA and down.

The 20W output comes from the same 600V supply and also goes to the output circuits of the B507. The difference is that this output is power limited to the 20W to 30W range. You can test this output with various resistive loads to make sure that it can supply at least 20W at a voltage from 5V to 500V.

There is a normal 37V supply, which is not grounded on either side. This supplies unregulated power to the B534 negative current regulator. This board is used by a test, Forward or Reverse, which uses a constant current of more than 4mA.

The FEC200 contains a 0-2KV test supply located in the same chassis as the operating supply. A DC to DC converter supplies the unregulated voltage for the shunt regulated output stage, whose output is controlled by a vacuum tube.

The DC to DC converter works only when a test requires its output. It makes a faint whistling sound as it operates. The 2KV supply has its own on-off switch so you can turn it off if you are testing only low voltage devices. It is not necessary to do this however.

Frothingham Electronics Corporation
44 Crystal Lane
PO Box 629
Wakefield, NH 03872-0629
FAX: (603) 522-9710
Phone: (603) 522-6620

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Last Updated September 12, 2007
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