Hi One of the trigger level pots is stuck at the 2 V end of it's travel. That's making checking things a little difficult.
The 5345 inputs were pretty easy to blow as I recall. Bob On Mar 9, 2010, at 7:03 PM, Mark Sims wrote: > > I've had the "pleasure" of fixing way too many 5370A and 5370B front panels. > It's been a while so these musings may be clouded... also beware of the two > or three different front panel designs. Also there are "hybrid" 5370A's out > there with 5370B front ends. > > There are 4 pots on the front panel: the 470K display update rate, a 10K or > 200 ohm arming level (200 ohm on 5370B and later 5370A's), and two 5K > trigger level. All are linear taper, all have switches, all are small pots > with (1/4"? bushings). Finding pots with proper switches ain't easy. > > I have never had to do the trigger level pots. They have metal shafts and > seldom break. Their switches are what you would expect (closed when the pot > is turned clockwise). In the far CCW direction the switch is open and > selects the 0V trigger level. > > The other two pots are an exceedingly crappy hp design. They have fragile > plastic shafts and really poor quality switches. The switches need to be > closed when the switch is counterclockwise. HP's pots have both normally open > and normally closed contacts. Frankly these pots are seldom used and you > can use a switchless pot and just hardwire those pads. > > The display rate pots is particularly useless. You can just hardwire it to > max. > > The biggest bugaboo in buying a 5370 is the state of the HP custom input > amplifier chips. They can be damaged by overloading the input. Blow one > and you are screwed. Buy a 5370 with a blown input amp and you are screwed. > The 5370A and 5370B used different chips. The 5345A counter is a source of > input amp chips. > > It would be VERY nice if some clever person built drop in replacement > "chips" built of modern SMD parts on a DIP header. Those input amp chips are > socketed. They are little more than a comparator. > > Quick check of the 5370A inputs is to set the unit to "SEParate" inputs and > connect the back panel 10 MHz ref signal to each of the inputs. The signal > level LED should flash. A steady LED means that input is toast (or the input > PCB slide switches are full of navel lint and need cleaning). > > _________________________________________________________________ > Hotmail: Free, trusted and rich email service. > http://clk.atdmt.com/GBL/go/201469228/direct/01/ > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
