Reply with quote #16
Looking at your latest picture it does seem that the green and yellow wires are correctly connected. As you do not appear to have shortened these wires their paths were very difficult to trace in your earlier pictures. Make sure the gray wire from the timer board and the second green wire from relay terminal 13 do go to the correct pins on IC4. Green to 1, leftmost, gray to 2, centre. Kelvin
Reply with quote #17
Hey Drew, if the cap is swollen or the top bulging it almost has to be due to it being installed backwards or it had the connections to it backwards.
An easy mistake to make and/but it may have nothing to do with your problem if in fact the mistake happened. I only mentioned it because you said something about ....... " Tonight I was checking everything and noticed that the 10000uf 6.3v cap on the relay socket is definitely pushed up. (blown?)' A cap with the top bulging is not good! Keep at it....you'll get her fixed! Ed
Reply with quote #18
Thanks Ed! I"m not giving up.
Here is a comparison of my board and the board in the instructions: The gray wire is in a different spot. My board has a white jumper wire. Maybe that gets the connection to the same trace as in the picture. The cap is oriented with negative lead in the same spot so doesn't appear to be installed backwards. Thanks Attached Images
Reply with quote #19
Drew. Yes, keep at it; you will get there,
! A few further thoughts. If the 10,000mfd capacitor is blown then of course it will have to be replaced. In the mean time it might be better to remove the timing board altogether, and take out the relay. The non-working left channel consists of V2 and V4. V2 gets its heater supply from IC4. The timer board gets its supply from pins 1 and 2 of IC4. You say that all tubes light up and get warm. Do V1 and V2 look equally bright and are both halves of V2 obviously lit? If so you should check all wiring in the left channel; V2 and V4 nearest the edge of the chassis. I would also check the diode connections on tagstrip T3 which feeds IC4. Ideally you should check voltages against each other for both channels, but I realize you may not fancy working on the live chassis. I suppose that there remains the remote possibility that the timing board you received was faulty, but I would have thought that to be rather unlikely. Many have gone down this path before you. The MP is a very fine piece of kit. It will not disappoint you. Good luck. Kelvin
Reply with quote #20
And Ed and everyone else who helped and encouraged me. I decided to remove the board and relay completely, and all the signal path connections to it. Now my MP sounds AWESOME. Apparently my wiring and connections were correct all along. I'm proud of that. So, I will leave the relay and board out of the circuit altogether. It seems to complicate the signal path without adding a lot of value in my setup. I'll turn on the MP first and let it warm up before turning on my amps. As a result of this experience and your advice, I understand how this amp works much better. It's really not as complex as it seems when you are going step-by-step building it. Thanks again. Drew
Reply with quote #21
Originally Posted by
Drew Thanks Kelvin! I decided to remove the board and relay completely, and all the signal path connections to it. i'm just a lurker here trying to pick up what I can in lurkmode. (T8LN,GG,PowerFilter owner) Wasn't that Bruce's first suggestion? Pull out the relay and see if the sound comes back? We do that a lot in computer programming domain. When there is a problem, comment out suspect code blocks (where possible.) To isolate the location of the fault... Of course we can insert "debugging" artifacts into a program to capture the state of the variables at pretty much every step along the sequence of code execution patsh, so that is a little different than a real time circuit where voltages are dynamic...
Reply with quote #22
Yes, but I understood Bruce's initial suggestion "pull out the relay" to mean pull the relay out of the socket, on top of the chassis externally, as opposed to completely removing the relay and board and wiring.
Thanks again. I appreciate all the help.
Reply with quote #23
by the way, holy cow, this thing sounds AMAZING. wow. I can't stop listening to it.
Reply with quote #24
Drew. Excellent work! Glad you like it!
. A very mild word of caution about leaving the relay/timing board out on a permanent basis. Its function is, as you clearly realize, to protect the connected power amp from undue voltage transients on start-up, or if the power is interrupted for a short time. This is really only of significance when using some solid-state power amps. The directly heated output tubes in this preamp heat up quite quickly while the indirectly 12AU7s do so more slowly. Just make sure you switch on the power amp last and off first. Having removed the timing board you can probably figure out how it works and repair it if you feel that to be worthwhile. Again, congratulations. Persistence always pays. Bruce does make good stuff! Cheers, Kelvin
Reply with quote #25
Yes, duly noted on the turn on order. Thanks again!
I still don't understand what caused the problem with my relay and timing board, and what caused the cap to blow, since it was wired in correctly. I'm happy to have it removed from my circuit though. It was creating a bad signal for sure. If relays are potentially problematic, I'd rather be careful with how I start up and turn off. No big deal. This amp sounds so clean and clear! It's very powerful and the highs are so clean and sweet sounding. Maybe it's getting better as my tubes burn in. I'm very impressed with it. I built it too! I left the relay on top, unwired, for decoration.
Reply with quote #26
Found this to be very interesting I always have to turn on my amp after the timing circuit and relay have kicked in otherwise I get a loud thump I wonder if my timing circuit could be faulty?