More resistance readings for the Stock Foreplay Preamp
(Based on the 12.6V filament version of the Foreplay)

A few more Foreplay impedances to check during a debug process. Make sure the power cord is unplugged, the capacitors are discharged and the tubes are disconnected when making these readings.

Measure 1K from 2 to 7.
Measure 2k from 2 to 10, 2 to 11, 2 to 12 
Measure 300-400 ohms 4 to 5.
Measure 12 to A1, 12 to B1 = 120K (This will not read correctly with the anticipation upgrade installed.)
Measure A1 to A7, B1 to B7 = zero
Measure 11 to A6, 11 to B6 = zero
Measure 12 to B9 = about 100K to 200K (150K nom)
Measure A4 to A5, B4 to B5 less than 3 ohms (Short your meter leads together before making this test to check your meter out. With shorted leads, your meter should read less than 1 ohm to do this test. Some meters read higher than 3 ohms with shorted leads.)


A link to the Quest's Foreplay debug page
 Quest's debug info.
Quest's debug (Via Archive.org) info.

Which is better, a DVM or a meter with an analog movement?

For use in circuits with capacitors, an analog movement usually works better. You can set the range where you want and it eventually the reading settles in. A DVM can get caught up in an infinite range changing loop. If your DVM has the option to not autorange, use this option when measuring resistors that are attached to capacitors.

Also, many analog movement meters drive the circuit with a bit more current that helps charge the any capacitors up.

A DVM is nice for reading resistors because it is fast, accurate and usually harder to blow up. Ask Santa for one of each. Is use my DVM the most. But I occasionally pull out my analog movement meter when a large capacitor is driving me nuts. . . I mean driving the digital meter nuts. 


More Debug hints for the Stock Foreplay if you have resistance check problems

All of these tests are done with the 115V unplugged, the capacitors discharged and the tubes removed!

If you have low resistance problems on A1, A6, A7, B1, B6, B7, 12, 11, 10, 7 or 2, check the polarity of your capacitors and diodes. The negative side of the capacitors needs to go to ground. A backwards diode can cause a problem here too. Note: sometimes the capacitors on these lines take forever to charge up and cause a low resistance reading.

If you are still in doubt, buy a 1K 1/4W resistor, a 9V battery and a 9V battery clip. Leave the 9V battery disconnected for now. Tack solder the battery clip leads to terminals 10 and 14 with the 1K resistor in series with the battery clip lead going to terminal 10.  (Tack solder means to lightly melt the lead into the existing solder or use just a little solder to attach the lead to the attachment point. DO NOT make a permanent secure mechanical attachment. Just solder it good enough you can lightly tug on the leads and the leads stay attached to the solder joint.) This is not mandatory, but if the set up looks like something could short out, put a piece of tape over the + battery clip to resistor solder joint.

+ goes to 1K resistor, 1K resistor goes to 10
-  goes to 14
Attach your meter + to terminal 10 and - to terminal 14. Put on safety glasses, and attach a 9V battery to the 9V battery clip.  If you do not get an 8.0 to 9.5V (8-9V in short hand) reading a few seconds after you attach the battery, REMOVE the battery. If you don't get 8-9V, you have a short somewhere.

After you get 8-9V on terminal 10 to 14, you should get 8-9V on terminals 11, 12, 7 and 2. If any of the readings are low, you could have a bad solder joint, a short or a reversed capacitor or diode.

After you get 8-9V on terminal 2, read and write down the voltage from 10 to 14. You should get the same voltage on A6 and B6. You should get about 0.1 to 1V less on A1, A7, B1 and B7. (The voltage drops because of the meter loading. A 1 meg meter drops the voltage about 1V. A 10 meg meter drops the voltage about 0.1V.)

Leave the meter connected, remove the battery and it should take longer than 45 seconds (82 seconds calculated on stock Foreplay) for the voltage to terminal 10 to 14 to drop from 8V to 4V. (With the Anticipation installed, it should discharge in about 10 seconds (13.8 seconds calculated.))

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First issue 12-Nov-00, last update 15-Nov-00. 
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