I just purchased a used Dyna 400 and need some help. I don't have a
parts list or even a schematic. So, my problems are compounded. But
here goes. There is a small circuitboard mounted on the front side of
the huge transformer. On this board a 2 large power resistors, R307 &
R308. I need to know what the resistance values and watt ratings are
for these 2 resistors. Can anyone help??
Pete, I would be interested in hearing more about your Dyna 400 after
you get it working. Also, if anybody else has any comments about the
400, I would like to hear them. That's one Dyna amp that I don't have
any experience with. Please let me know how you like its sound
compared to a tube amp. Thanks. Bill Crowell
> Pete, I would be interested in hearing more about your Dyna 400
> you get it working. Also, if anybody else has any comments about
> 400, I would like to hear them. That's one Dyna amp that I don't
> any experience with. Please let me know how you like its sound
> compared to a tube amp. Thanks. Bill Crowell
I have 2 Dyna 400s that have been maintained over the years, and were
still working fine (for Dyna 400s) the last time I powered them up
which was a couple of years ago.
One of my Dynas has MJE 15002x outputs, and recalibrated SOA circuits,
because without mods, these amps are not the best choice for driving
very reactive loads. Hence the 416.
> I already did. That site doesn't answer my question - in fact
> nothing there regarding PC Board #30 or the 2 resistors I'm
> Can you/anyone tell me the wattage and resistance values for R307
is highly incomplete. The markings on mine are indistinct. They run
They provide the regulated power for the op amps on the input boards,
the input buffers & etc.
I believe that they drop about 70 volts. Current through them seems
to be about 10-20 mA. Resistance is probably about 3,500 ohms. They
probably dissipate less than 2 watts, so 20 watt parts should be
pretty good. If they are too low of a resistance the zener diodes will
run hot. If they are too high of a resistance, the zener diodes will
break regulation and not have enough voltage drop across them. I
think the zeners are 13 or 15 volt parts.
I checked the owners manual I have for a St-400 and it lists R307, r308 as
850 ohms 10watts
<firstname.lastname@example.org> wrote in message
> I think there was a conversion kit, or the equivalent, from Sound
> Values. They were a difficult bunch to deal with though.