Another new amp - motorboating

[MatthewShadwick]

Just received my tubes for my amp - put them in turned it on and I got a bit of a sqeal and some motorboat put put noises! - Any suggestions? I am just about to check my wiring.

Cheers
Matthew

[markh]

Check your layout carefully. Motorboating normally only happens when the filter caps are old - are you sure it' not tremelo beating you're hearing? Try removing V1 and then V2 and see if either of those stops it - this will give you a hint about where to look for wiring errors or faulty components.

--mark

[Graydon]

Also, check for the 220K resistor on V3. I forget that one occasionally and it causes the trem channel to beat and tick.

[MatthewShadwick]

I removed the preamp tube for the trem channel (V3) and fired the amp up again. No more put put noises! I plugged my guitar in and I must say that the tone is sensational. I must now look into what is wrong with the trem channel. I have built the amp as a 2 x 12 with celestion greenbacks. I have used purple tolex and oxblood grill cloth. I am looking forward to getting the trem channel up and running.

[MatthewShadwick]

I have found that I have some shielding issues on the trem channel. Last night I resoldered the wires onto the V3 socket. I am going to substitue the wire I have used for pin 7 with shielded cable. I managed after a bit of fiddling to get the channel working really well and discovered that I had not made any mistakes with the wiring. I can see why people seem to have issues with this one. Once I have fixed it properly, I will take some pics of my solution.

Regards
Matthew

[MatthewShadwick]

I now have the trem channel working properly and I must say that the trem on this amp is fantastic. My solution was to run shielded cable from pin7 on v3 to the board as well as to the foostwith connector. I am using an RCA connector for this instead of hardwiring the footswitch into the amp.

[Moose]

Thanks for the report.

I've got a similar problem with my bizarro 18watter's trem and the first thing I considered was shielding leads. Haven't done it yet, but it's nice to know that that's a good place to start.