amc
Head-Fier
- Joined
- Apr 18, 2009
- Posts
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Quote:
Quote:
Originally Posted by amc /img/forum/go_quote.gif
Hi Tomb / Equalizer,
I checked. Tip is the red wire in the following pictures and its going to the B+ pad. I even reversed them and tried again and I get the same measurements just negative instead of positive. Here are a bunch of angles of the top and sides of the board. Did not detach the heatsinks but can if need be for more pictures of the underside and to start removing parts - sigh...
I can't fault your work from what I see in the pics - you've done a good job!
However, it looks like maybe R13 is not soldered on one end - that's the resistor up against the power input terminal block. That resistor divides the voltage supply between the two tubes and may cause some of your symptoms if it's not soldered.
A second suspicion is your tube LEDs. Those leads look awfully fat. I'm not surprised that it took a pair of pliers to get them through those tube socket holes.You may have an intermittent short if forcing them through did some damage. If R13 or any other resistor doesn't check out (check them all - for value, too), you might try de-soldering those leads, put some electrical tape on tips and see if that makes a difference when you turn the amp on.
Take a look at those things and let us know.
So after gathering dust on my bench for the last 5 months while there was a ban on melting lead in the house due to pregnancy, my 2nd daughter Ava has been born. I pulled out this frustrating project and had a go at it with renewed enthusiasm and it is now working fine and sounds great. To close the loop on my troubleshooting and resolution here is what I did.
I followed the advise and painfully dis-assembled the heatsinks yet again to go over the bottom of the board with a fine tooth comb. I did find solder joint I was not happy with and for good measure reflowed a lot of the ground connections with a larger tip than the last time - this sped up heating the groundplane significantly! I re-did the LEDs with thinner wire and re-attached the heatsinks and still nothing. Cr*p!
So I started probing again and found the problem - so simple! I did not have continuity between the switch wires regardless of the position of the power switch. Checking closer I determined I did not have a good connection between one of the fast on connectors and the wire connecting the switch to the board. So I removed the switch and jumpered the switch connection and the LEDs powered up, the tubes started to glow and the amp worked.
Moral of the story - take small steps and eliminate the easy things before you just to conslusions. I could have saved myself a tonne of pain! Thanks to Tomb and the_equalizer for helping me out.