found a chassis in my storage place :D

[erwin_ve]

Thanks, I guess the light reflection is making it look like there is a pinstripe in it. Looks good!

You're looking at the carpet through the speakerhole and backplate hole of the cab.

[martin manning]

I see that, It's the vertical stripes I was wondering about.

[talbany]

It's called Pinstriped Snakeskin

Cool!!

Tony

[norburybrook]

Well a marathon session today and I think its all done...lordy lord, that's a lot of stuff to cram in there.....

I'll do my ground checks etc tomorrow then fire up....oh i need to make the footswitch as the FET wont work without it.


Beer O'clock i think...

IMG_20191110_175039-01.jpeg

IMG_20191110_175106-01.jpeg

M

[martin manning]

Cliffehanger.

[j0k3335]

... you found a chassis the Oct 18 ... and the amp is closed to be complety build ( ... and really well ) the Nov 10 !!!

less than a month ! I am stunned! (I wish really to have such skills !!! )

So congratulations ... and I look forward to the first tests, the first adjustments, the last small changes.

... anyway : well done!

[norburybrook]

... you found a chassis the Oct 18 ... and the amp is closed to be complety build ( ... and really well ) the Nov 10 !!!

less than a month ! I am stunned! (I wish really to have such skills !!! )

So congratulations ... and I look forward to the first tests, the first adjustments, the last small changes.

... anyway : well done!

thank you as I always say..if I can do it anyone can

the next bit can be incredibly uplifting or frustrating depending on what happens on power up Last 2 amp's I've built have been very simple (princeton reverb and a trainwreck express) so worked first time on fire up.

I'm expecting Issues with this build as it's so complex compared to those.

I will say, I've learned most from amps I've built NOT working on first fire up than those that did. So whatever happens it's all good tomorrow

this amp is a hybrid, hybrid so even if everything is wired correctly it still might not sound great ...or then again it might be awesome ....I love this part of it.


M

[didit]

I am exhausted just browsing those photos. It looks clean and correct to my tired eyes. Fire it up, wisely carefully.

Best .. Ian

[talbany]

Congrats Marcus your 1/2 way home

Here is what I generally do to for the smoke test for an amp w/Loop. FWIW. I call this more like a troubleshooting way of starting up. This way if I missed something I can easily and safely find it and isolate it while I am introducing voltage into the amp
BTW. I do this usually in a dead quiet room.

Throw the thing under the glass (Magnifier) and just do a quick scan one last time. Especially the PS.
Check that everything that should have a Gnd point does and ohm them out. (including Rectifier and bias and relay supply, filaments)
Check each node in the PS on up to the plates for any dead shorts to gnd or low Ohm readings.

Clip in your meter at the PS plate node and set it for DC volts and turn stby to off.
Slowly bring up the voltage to somewhere between 75 to 100VDC.
on your meter.
Unclip your meter or grab another one and check each node including the bias supply for active DC volts along with the filaments and relay supply. (You just want to make sure everything is coming up).If something looks too low or to high or not there? shut it down and figure out why.

Continue on with your meter back on the plate supply. I bring it up to around 200-250V. let it set a min and repeat the voltage scan again at 1/2 operating volts.
If everything checks out bring it up to the PT's operating voltage slowly listening for any strange sounds (Like arching). Stand away from the amp. After I reach operating levels fuses are still in tact and I let it sit a while 10 min or so. Check the PT temp.
Then it's safe to move in and go back over all your voltage points again. Check the bias voltage swing in both directions (at the pins on each socket) Make sure you have enough range both ways then crank the pot up to max -DC volts and check your STBY switch is working.
I generally let the amp sit like this for a while have a drink let the caps form in check my relays are clicking and my relay voltage is in range.

Power down and snap the caps. At this point I might disconnect the GNFB wire.
Load up the tubes
Fire it back up w/ speaker and bring it up slowly (with the master and return amp off and the loop jumpered with a patch cord in) this time with your probes attached to a cathode monitoring your bias current.
Check to make sure all the filaments are lit.
Pull your tubes out of cutoff and let them sit a few min and monitor for any drift. While your doing this you can go back and do another quick scan of you voltages (since they dropped off) check the PI's Grids cathode and tail voltage along with V1/V2/ and loop.
Check the loops plate voltage
Here I'll clip in my GNFB wire and make sure I am in phase. If so leave it clipped in
(with the amp on) bring up the loops send and the return levels. You should hear some level of hiss or noise something from the return amp.Here you can check the noise levels in the loop and the output section is working. (You can plug in your guitar to the return jack and check the loop's return amp along with the output section) If everything checks out and your noise floor is fairly dark plug in a guitar and bring up the amps input level and master and see how it sounds. Check all your switches and controls are working as they should.
Hit the relays check the OD side and all there controls are working ok. Also check your noise levels with the loop still in.
At this point I will check the STBY switch flip it off and on a few times see if it pops or blows a fuse.
Power down and solder in my GNFB wire again and don't forget to drain the caps if you go back in (which you will more than likely have to do several times). I generally clip a resistor to my alligator clips and have it on my bench each time I go back in. I generally do all this while monitoring my bias voltage in case something goes wrong and I can catch a red plate before it kills one of my tubes.
If everything looks OK I'll let it cook and monitor the temp on my power transformer make sure it does'nt get too hot along the way.

Always wear a good pair of rubber sole shoes and a rubber insulated mat under you. Don't do this totally alone make sure someone else is in the house and can check on you and have your cell nearby with an emergency button on it. Also have a fire extinguisher under your bench as well.

The most important thing I can say is. TAKE YOUR TIME!! we tend to want to hear how the amp sounds so we get in a rush here and make mistakes like forget to snap our caps. Along the way if you find something that does not look right abort the start up and figure out why?. If everything goes smoothly it usually takes me about an hour to complete everything including letting the voltage settle in the amp.

Anyway That's how I do it and has worked pretty good. This way you have a good chance of catching something off before the smoke appears or something blows. If someone sees something I missed speak up always want to learn a better way.

Good Luck!

Tony

[norburybrook]

Thanks Tony,

That's a very detailed, comprehensive start up I presume yo have a variac so checking things with a lower voltage first is a great and safe idea. Unfortunately I don't so the limiter is my cheap and simple solution to any main issues...shorts basically.

this paragraph jumped out at me though and is something I hadn't thought about so will bear in mind in future.

Always wear a good pair of rubber sole shoes and a rubber insulated mat under you. Don't do this totally alone make sure someone else is in the house and can check on you and have your cell nearby with an emergency button on it. Also have a fire extinguisher under your bench as well.

I shall report back later today after I've made the footswitch....wiring the footswitch DIN jacks ranks alongside heater wiring for me.....


M

[norburybrook]

still not fired up yet. Took me all day to make the footswitch what with everything else I had to to today.

I couldn't find a suitable enclosure for a 3 button. So I looked around and found a digitech 3 button switch which was cheap as chips. When I took it apart I realised I couldn't use the actual footswitches as they were over a PCB based switch. Even so at $20 for the casing alone it was fine. Drilled it out for the various LED, switches etc.

sprayed it up to cover the original graphics and wired it all up. It's a 6 pin DIN so I've an extra 9v cable to the socket on the F switch for pedals. I've left it un grounded as I'm thinking the pedal/plug will ground it, and this way there's less chance of a ground loop.

IMG_20191111_163338.jpg

IMG_20191111_163347.jpg

IMG_20191111_163410.jpg

fire up tomorrow.

M

[martin manning]

Nice compact foot switch. The ground will be interesting. Your pedal will have to be grounded with your relay supply now, won't it?

[norburybrook]

Nice compact foot switch. The ground will be interesting. Your pedal will have to be grounded with your relay supply now, won't it?

well that's the easiest place but I was thinking it would ground via the jack sockets somewhere not sure where exactly.......yet another experiment



M

[norburybrook]

I've been thinking about this over dinner...

the last time I did this I used the 9v connector and placed it o the back of the combo but I used a reverb pedal in front of the amp and not the loop so it grounded via the gtr jacks.

In this scenario with the FX in the loop it will need grounding somewhere ...so I'll have to ground at the relay ground inside the footswitch.

This amps has been a tale of grounds ~:D



M

[norburybrook]

Well, I think i deserve a little pat on the back with this.

I fired up today and EVERYTHING WORKED 100%. amazing...well it is for me...even got the OT primaries correct.

I've got about 190v on V1 and 209v on V2 which is great

I've got El34's in there with 452v so I've got it biased at 40/38mv

NO HUM

I wired the speaker jack with a cliff isolated jack, ran the OT to it and then grounded at the main filter cap ground bus.
Everything with the loop is star grounded on the loop tube tag.

IMG_20191112_132110.jpg

now then..there's a however........as always.

I now realise that Erwins boards for the realy rectification are NOT voltage doubles like the regular Dumble builds.......so my 9v pedal supply, well in fact the whole relay supply too is only 4v. Fortunately the 5v relays seem to work with this.

So, the million dollar question is: whats the simplest way to get 9v from my 6v supply?

here's Erwins board

Relay board.png

Am i going to have a to make another board? or buy a transformer with say 12v output?

remember this is a PCB.




M