new build is now happy

dcribbs1412 · Post by **dcribbs1412** » Tue Jul 12, 2011 4:11 am

M Fowler · Post by **M Fowler** » Tue Jul 12, 2011 4:23 am

What size fuse are you using? The inrush could be popping the fuse if too small.

Mark

crbowman · Post by **crbowman** » Tue Jul 12, 2011 6:23 am

Make sure you are using a slo-blow fuse.
I had to learn this one the hard way.

heisthl · Post by **heisthl** » Tue Jul 12, 2011 7:10 am

show a better picture of the main B+ diodes, bias diode and relay supply.
you should always run a new build on a light bulb in series with one side of the line voltage. This allows you to use your voltmeter to find the short, or in the worst case, allows you to see where the smoke wants to come out....

alvarezh · Post by **alvarezh** » Tue Jul 12, 2011 8:55 am

Hi, after the above items haver been checked, and if by any chance it's still blowing fuses, what you should do is isolate the circuit that is causing the problem. You will need a handful of fuses, they will be popping every time you fire it up before you finally isolate the culprit.

I would begin by removing all the tubes because it's the easiest thing to do. No more problems, you've got a bad tube. Reinstall each tube individually and power up the amp each time until you find your bad glass. Still blowing the fuse? put the tubes back on and disconnect the all the HT wires feeding the pre & power sections from the filter board. If it's still blowing, disconnect all the PT's secondaries, reconnect one circuit at a time and check. Remember that your problem could also be in either the bias, heater, relay power section, the rectifier board, the PT itself and probably the the OT (not sure about the OT) because the mains fuse protects the whole amp. Isolate and test.

Lets assume that after you disconnected the HT wires from the filter board the fuse didn't blow, then reconnect each wire back into the board individually and check. Hopefully the circuit that is causing the problem will blow the fuse.

If the problem is on the preamp board, then disconnect all the plate load resistors from V1 to V3, or, if you prefer, disconnect the plate wires at the tube base and recheck. By now the fuse should not burn. Reconnect each plate resistor (or wire) one by one until you find the one that burns the fuse. If, on the other hand, the fuse did burn, then I would suspect a problem with the heater circuit. If that is the case, disconnect the heater wires at V3. Still burning the fuse? reconnect these wires and disconnect the power tube heaters from the PT. Still popping the fuse? most likely a bad heater winding on the PT, there is nothing else left!

This is not by any means the only way to check for faults, it's just a few procedures to get you to going, it has worked for me. Hopefully some of the more experienced troubleshooters can chip in, I am always in need of knowledge myself!

It's a lot of testing, so please don't rush and DO remember to flush your caps!

Again, the main idea is to isolate the problem circuit so you can start checking for bad components, solder joints, shorts, misinstalled connections, bad transformer windings, etc.

As the Romans used to say: Divide and Conquer!

Hope this helps.

T Wilcox · Post by **T Wilcox** » Tue Jul 12, 2011 1:10 pm

I dont see any obvious causes to your problem on the pics but I did notice the wire connections in a few places such as your IEC connector are just inserted then soldered, which is just asking for trouble. All connections should be wrapped around the terminals crimped with needle nose then soldered. They should have a good mechanical connection before the solder is even applied

Todd

67plexi · Post by **67plexi** » Tue Jul 12, 2011 1:40 pm

It may be your bias is way off not sure.

I had this with the cheap CTS 10k bias pot all full of carbon dust inside

the master of sparks inside. will never use a CTS 10k pot after that.

using a variac and blowing over 10 slow-blow fuses I tore it down.

After that the first thing I do is the power supply.

I could be wrong but in China I would be Wong.........

dcribbs1412 · Post by **dcribbs1412** » Tue Jul 12, 2011 2:43 pm

Thanks guys really appreciate the help
I am using 3A slo blo
no tubes in...
I will redo the wiring...wrapped around the terminals crimped...when
its up and running

more pics

http://i1018.photobucket.com/albums/af3 ... 183017.jpg
http://i1018.photobucket.com/albums/af3 ... 183019.jpg
http://i1018.photobucket.com/albums/af3 ... 183020.jpg
http://i1018.photobucket.com/albums/af3 ... 183021.jpg

with no tubes would the bias pot cause this Wong?

Will start ...Isolate and test.... ASAP

Again any comments are greatly appreciated

Darin

T Wilcox · Post by **T Wilcox** » Tue Jul 12, 2011 2:56 pm

Update us on what you have tried so far.
Has it blown a fuse with no tubes?

Todd

Zippy · Post by **Zippy** » Tue Jul 12, 2011 2:58 pm

alvarezh wrote:I would begin by removing all the tubes because it's the easiest thing to do. No more problems, you've got a bad tube.

Not true. If this is an initial startup, removing the tubes can also open the circuit of an improperly wired socket. One needs to remove the tubes and check voltages on the pins to ensure correct voltages at the right places.

alvarezh · Post by **alvarezh** » Tue Jul 12, 2011 4:38 pm

Absolutely right Zippy, thanks for clearing that up. I thought about it after I posted, it was 4:55 am, had not not gone to sleep yet and I was fighting to keep my eyes open.

Besides, I have to keep a watchful eye when giving advise on newly built amps as opposed to a perfectly working amp that has broken, there are more things to look out for.

Anything else? don't want to throw dcribbs or anyone off!

Thank again,

dcribbs1412 · Post by **dcribbs1412** » Tue Jul 12, 2011 5:47 pm

Hi guys
thanks for the replies

Update us on what you have tried so far.
Has it blown a fuse with no tubes?

yes blows fuse with no tubes

Darin

Zippy · Post by **Zippy** » Tue Jul 12, 2011 6:13 pm

Well, at least that narrows the field of the search.

T Wilcox · Post by **T Wilcox** » Tue Jul 12, 2011 7:11 pm

Possibly a dumb question, but is your power light rated for 120v, just ask because the ones Ive built use the heater 6.3 as well as the 183 layout here

What is the model/part# on the PT you are using?

If the PT has a CT for the heater, do you still use filament resistors?

Todd

glasman · Post by **glasman** » Tue Jul 12, 2011 8:10 pm

Where in AZ are you located?

You can always stop by and I can help you troubleshoot the problem.

Gary

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