Zener diode testing?

[radiogaga]

Working on GLA 1000 amplifier, has no idle current.
Tested bias Zener with dmm. on ohms scale.
5.6 Meg ohms one way, infinite w/ leads reversed.
Good or bad...?

Thanks
rgg

[redhat]

Sounds normal.  Best way is with an adjustable bench supply and a suitable dropping resistor, maybe 10K.  Ramp up the supply while monitoring the voltage across the diode.  It should keep rising until you reach its breakdown voltage, then stay there as input voltage is increased.

Keep in mind if the diode is backwards, it will function as an ordinary diode with a 0.5~0.7V forward drop.  You can verify this with your DMM on diode check.

+-RH

[radiogaga]

Thanks redhat,
I will reinstall zener and key amp and measure voltage drop, changeover relay is an obvious replacement and probably burned  contacts.

rgg

[skeezix]

Sounds like the classic black-hole diode-

Another new addition in the small-components market is the 7N-∞ BHD (black-hole diode). This device has two inputs and no output. Care must be taken to shield this component appropriately or it may absorb the unit it is placed in. The 7N-∞ will accept any voltage or current value. It is useful for GI (garbage-in) applications. Due to the light-absorption qualities of the device, we could not provide a photograph. Contact Spatial Regression Ltd, POB 463, Paulborough NH 03458.

http://aprilfool.s3.amazonaws.com/1981blackhole.jpg

[radiogaga]

Well the diode has bias voltage but the meter mult-switch only works on plate voltage.other contacts are toast, is this a suitable eBay replacement for voltage current and relative power out?
https://m.ebay.com/itm/2-Pcs-20mm-Shaft-Length-2P3T-2-Pole-3-Position-Band-Rotary-Switch-/122687082022?epid=1139450437&hash=item1c90b84e26%3Ag%3AinUAAOSwFqVZriZG&_trkparms=pageci%253A5c0234ba-b532-11e7-be9f-74dbd180728c%257Cparentrq%253A374da1af15f0abc3208b47fafffff368%257Ciid%253A9
Here is snip of schematic :
Thank you

[redhat]

It looks like the switch does more than those three metering position.  Front panel shows off-standby-volts-current-relative output.....that's 5 positions and judging from the schematic at least a three deck switch.

More research needed.

+-RH

[radiogaga]

Those two spst contacts were separate mounted on rear of wafer, shot  and abandoned.
On off is now toggle switch and stand-by is not needed.
rgg

[redhat]

In that case, those wafer switches should be fine.  Mouser and digikey should have other options as well.

+-RH