-=> Roy J. Tellason said to Mike Ross
 -=> about "BAG OF CHIPS" on 01-12-04  12:06.....

 RJT> yet,  they didn't even switch by decades or anything.  So finally I ran
 RJT> across a chip which would do it (the number escapes me at the moment). 

Hmmm... the number 3038 comes to mind, but i can't find any data
sheets to check it.

 RJT> Here's the thing,  though -- you get real low in frequency,  and all

How low do you mean by "real low"? Below 100Hz, 10Hz, 1Hz?

 RJT> of a sudden the output waveform gets *real* distorted.  Sine or
 RJT> triangle waves have a chunk out of the middle of the top part.  I can't
 RJT> recall offhand what squarewaes do.  I showed this to one guy,  and he
 RJT> said to me "get that power supply out of the box",  but it being a

I wonder what he was thinking of -- interference from the power
supply, or did he just want to have a look at it?

 RJT> transformer and the rectifier and filters being on-board,  that's a
 RJT> little difficult to do.  I did add more filter capacitance at one
 RJT> point,  and that didn't help much.  I think that what I'm likely to try
 RJT> next is removing the zener diodes that are in there currently and
 RJT> sticking a couple of 3-terminal regulators in there instead,  since I
 RJT> have them on hand.  Along with associated caps and such.  Other than
 RJT> that,  I don't know... 
 RJT> You guys have any ideas on this?

I suspect you might be running out of current in the power
supply. You mention that you are using zener diodes -- I'm
guessing that you have series limiting resistors to feed the
zener regulated output. So the output stage can't pull any more
current than the series R will allow to flow.

Since you obviously have some way of looking at the waveforms,
what do you see if you put the CRO on the power supply lines to
the unit? I'd look at the lines both before and after the zener
regulators.

Where did you connect the extra filter caps? Were they before or
after the zener regulator?

Yes, by all means use 3 terminal series regulators. They are so
cheap and they will supply all the current you need, within
reason.

From Greg Mayman, in beautiful Adelaide, South Australia
   "Queen City of The South"    34:55 S  138:36 E

... Headline:  Police Begin Campaign To Run Down Jaywalkers.
___ Blue Wave/386 v2.30

--- FLAME v2.0/b