The Amp Garage

It means your output primaries are swapped with each other. I've swapped my output primaries so they were not squealing with the 'working' config but no bias on V4 reading. how would swapping the valves round affect the OT primaries phase? just to make sure I swapped them , and re connected the NFB...

I think it would be good to take it to a tech. Where are you located? South London. Techs are very expensive here. I've not seen many times of reading this forum when taking to a tech has been cited, may I ask why in this case? I was hoping to sort this out myself with the help of you guys here :D ...

Progress :D I fitted the grid stoppers. I fired up the amp in it's working state. Still no bias resistor reading. Swapped the valves over...Squeal city again. removed the NFB wire from the speaker output ......no squealing, and I could get a bias reading from V4 at last :) amps plays fine though the...

JazzGuitarGimp wrote:Looking at your PI voltages, I see you haven't reported a voltage for pin 5. Is pin 5 tied to pin 4 ?

yes it is.

just putting in the grid stoppers as we speak.

Marcus.

I put the Kt66's in my bandmaster and they seemed to work however, it's just weird that when I swap them round I get the terrible squeal. Are you saying that swapping positions with the KT66s IN THE BANDMASTER also squeals? Based on the fact that when you put 6L6s in the Marshall you were able to g...

Do I ground them to the same point the bias resistors are grounded to by adding a length of wire? Neither end of the grid stopper resistors will connect to ground. Unsolder the wire connected to pin 5. Connect one end of the resistor directly to pin 5. Connect the other end of the resistor to the d...

Morning chaps, Ok I've ordered some 1.5k 3w resistors from maplins and am picking them up later today. I realise when yo do this a lot you'll actually have supplies of a lot of regular value resistors to hand. I have to order them! This was all they had hence the wattage. Do I ground them to the sam...

Why are you using pin 6,as it is not hooked up to any section in the tube! What is your voltage on the plates of the phase inverter section, as I see you only have 400 volt rated caps there? In fact for now let's disconnect the input cap to the PI section and just deal with the output stage and pow...

Hi, The resistance is measuring the expected 1R across both resisters so that's fine. OK voltages to ground: V4 1: 2: 3.19 AC 3: 450. DC 4: 454 5: -53 vDC 6: 452 7: 3.19 AC V5 1: 2: 3.18 AC 3: 447 DC 4: 452 5: -53 vDC 6: 455 7: 3.19 AC I don't have any resisters of the right value to put in as grid ...

Thanks guys, appreciate the help, as someone new to all this it can be a bit overwhelming when things don't work. However I'm sure I'll learn a lot more form sorting this out than if it had worked first time :) @jelle I'll have to take all this in and go through what you said slowly :) I'm still pai...

Ok, today I swapped out the KT66's for a pair of 6L6's which were the only thing I had to hand. I can now get a reading on V4 , so with that in mind I biased for these valves around 34mA to check things. I've now got serious motorboating. Does this mean my valves, or at least on of them is bad? Put ...

Hi, I'll start by saying I'm a newby at all this so have read a lot here but not posted. Ok I've built my first proper amp a JTM45 using various layouts from this forum. It's all built and I was trying to Bias the amp properly after installing the Shuguang KT66's and playing it for an hour or so. I ...

Wow, even though a lot of this info is over my head (not for a long though), I got a taste of what it takes to get to the best tones in industry. I will keep rereading your posts ( I even printed some), but my question is , what does "Lead dress" mean? Quick, let me jump in here, as a novice at all...