The Amp Garage

thanks again for your help Martin !

I changed once again the V1 and V2. actually... thanks to the last mods, now the amp is very quiet, quietest then my Express :oops: And, by the way, it sounds amazing !!! :D Here's the pair of winners: This PCB-Liverpool is the upper one, into a custom-made cabinet. The old Ford Monterey nameplate i...

The last mods: -replaced all resistors around the V1, as well as the two 22uf. (Parts are from the leftovers of a Ceriatone kit) -changed the presence layout for the same as on RJ's build -removed the 2 solder points on the potentiometers (ground loops ?) -modified the bright switch: I kept only the...

47k should be more than enough. You can try replacing the plate resistors, but I find that the biggest driver is the tube itself. Ok I will try replacing the plate resistors... Regarding the tubes, I tried 5 differents (good NOS that I know they are quiet, some modern ones, and 12AT7 as well). More...

martin manning wrote:I would try replacing the plate resistors on V1 with MF type first, but what values are the grid stoppers on the first two stages?

Grid stoppers are both 47k on V1. On V2 I have a 22k

Is it still the case that the hiss stops when you remove V1? yes it is Which controls affect the level of hiss? only the GAIN. Nothing changes with the bright switch, nor the 3 EQ pots. Of course it increases with the master volume ... EDIT: In order to exclude any cold solder joint, I re-soldered ...

well, I double checked all the resistor values, I also redid these solder points, just to be sure... I tried others preamp tubes, and it seems to work better now. Actually, all the tubes I had in this packages was bad !! So, now with good preamp tubes (I tried 2 or 3 differtents in each position), o...

After some tests: -All the connections to ground are ok (less than 1 ohm) -I if remove V1, no more hum, nor hiss. -Only the GAIN potentiometer does affect the hum. -See my Voltage chart below, the V3 voltages seem to be wrong ?!?? [img:116:165]http://img4.hostingpics.net/thumbs/mini_801900Voltages.j...

Ok... I doubt that will fix the hum, but I will try to ground it as you did...

And do you think the presence wiring or the 1k/25w resistor location would be the cause of the issue?

well, any thought regarding the yellow/white grouding ?
And the 3 others points above ?

Hi Rj, I just see one thing on your build: just under the standby switch, did you ground the white/yellow wire ? I did not, could this be the issue's reason ? Actually, I can identify 3 differences between our respective builds: 1. Euro voltage PT 2. I wired the presence pot according to the Liverpo...

Thanks Martin, you are right, one of the EL84 is defect. I just tried with another tubes set and it works !

Here's my half-liv PCB:
[IMG:165:123]http://img11.hostingpics.net/thumbs/mini_225244liv1.jpg[/img]

It works but there is a big "hum" and a little hissss. Sounds like ground loop or something, however the ground points seem to be as good... any idea ?

Hi I just finished a Rj's PCB Liverpool, but I have some problems to power it up properly. 1. Bulb limiter, no tubes: AC power OK, heaters OK, PT secondaries OK, all B+ OK. 2. I double checked all the connections, the layout, etc... All seems to be fine. 3. Bulb limiter, tubes installed : asa I swit...

I have to say that mine did not work well, because of vibrations and layout changes... today this amp does not exist anymore. I built a new one (head) which works very fine

[img:400:281]http://ampgarage.com/forum/files/thumbs/t_103_157.jpg[/img]