correct.
but the resistor drawn is just symbolic of the load of course. the junction of those diodes goes to the first filter cap +.
if i were to use a SS rect, i would add in a standby switch, to let the heaters warm up before dropping the B+ on them, but that's just me.
e
yes, resistor is my load, standby s/w is a good idea, the valve's will last a bit longer, if i dont blow it up messing on with it, lol,
hey i had a look at your voltages while doing the kids swimming run-around. you seem to have a problem with your power supply. your B+ is too low, and the calculations don't show either of the valves pulling heavily to bring it down. your idle current reads as 28mA.
is the trans the same one you are looking at running with a SS rect? 350-0-350?
with that kind of HT and really only a single 6v6 for load, a 5y3-gt should give you a B+ of about 400VDC. (i see your layout the rectifier noted as a weber copper cap, so not sure what you have there. personally with an amp like this i would stick with the 5y3).
also not sure what you mean with pins 4 and 6 reading 120v. is this DC? AC? between the points or seperately to earth? whatever it is it's funky anyway.
remove all three valves and turn the amp on, and post the VAC readings between pins 4-6, and 2-8 on the rectifier socket.
turn the amp off and replace the 5y3. turn on and again check ACvoltages between 4-6, and 2-8, and DC voltage from 2 or 8 to the chassis ground where the centre tap is. post those too.
turn off. put the 6v6 back in. turn on.check those AC and DC voltages again.
just checked voltages on a very brown champ style amp i have here with a low HT of 254-0-254, and that gives a B+ of 305VDC. also checked a 6bm8 powered amp a built a while back that has a higher 355-0-355 trans, that gives a B+ of 415VDC, and that's with a big coke-bottle 5y3 i used to bring the B+ down a bit.
those readings should tell you where the problem is.
e
eric, the 4-diode voltage dropper only dropped the voltage by 0.2v, ???
well after messing with it for week's off and on, i was sat looking at a pic of the original fender champ amp gut's, and i thought if it worked ok like that i'd give it a go, bingo, work's fine no hum, buzz, squeal, i'm really pleased, i used all the same component's tranny's etc, so i dont know what was going on with the tagboard set up, but i dont care, i've built an amp that work's, yippie,
what i need to know now is what can i alter to get it to break up/distort a bit sooner, it seem's very clean sounding to me, any thought's,
and thank's again for all the time you've put in helping me, i'll still probably have lot's more question's as i move onto some more complicated circuit amp's,
that's great news, and a very tidy job i might say.
too cleam? earlier breakup, hmm. a salvaged low power paper cone speaker from a radiogram might be a good place to start experimenting, just check for impedance match with your OT.
valve swap - try a bunch of 6v6's and swap out the pentode too if you have any around.
you might want to change the bias on the preamp tube? you could wire a 5M pot in series with the 5M grid leak to see if things change much. this bit of the amp is low voltage and current, so a normal pot would be fine.
i have heard of some folks subbing the 6v6 for a 6k6 or 6f6. all have the same pinout, but the k and f will handle less power, but in the case of the 'F' it is more sensitive. you can find at least the f in a coke-bottle shape (6F6-G) which seems to be even less efficient. if you do change the type of power valve, be sure to check your voltages and rebias to suit - this will involve measuring current through the valve, voltage across the valve and working out power through, and changing your cathode resistor to get the numbers right.
you know.. V=IR and P=IV.
great to hear it's all going well now.
e
thank's eric, i'll give those suggestion's a try,,
Well done Garage Hermit - when do we get to hear it on video?
think the wife's camera does video, i'll try and figure it out,
oop's,,
made another one, but this one has a 10" speaker and s/s diode rectifier, sound's better than the last one, probably the bigger speaker, no hum, buzz etc,
thank's eric, could'nt have made these without your help, i'll have to try and spread my wing's and make something a bit more complicated, there might be a lot more question's though, lol,
cheers fella,
you have obviously gained much by struggling through that first one. this lastest is very tidy indeed. you are most welcome to any help i have given.
with these little amps, the sensitivity of the speaker is a big part of the break-up sound (and the overall output level). perhaps this speaker it more efficient?
as a by-the-by, just looking at your turntable amps, it's great that they have the output trannies on there, but how do you know what kind of load they transfer? there is a pretty simple but sightly scary test procedure using your mains through the primary which works a treat. it's too involved to put in here, but morgan jones details it in his amazing book "valve amplifiers".
the book isn't about guitar amps but has more info that you ever wanted about valves amps.
treat yourself!
e
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