My new build ,high volyage readings

[danman]

Well it sounds as if you are getting good B+ voltage and I am assuming that the fuse does not blow when you switch the standby into play mode. You need to take some DC voltage readings at pin 3, 4 and 5 of both power tube sockets. You can leave your preamp tubes in but do not install the power tubes. Set your meter for the highest DC voltage scale and switch the amp on fully into play mode. The meter's black lead will go to ground and take readings at each of the three pins that I mentioned. Please be careful here as the voltage will be close to 500vdc. It may help to have some clip on meter leads to avoid any slips. Let us know what readings you are getting from these pins on both sockets.

[fixer2]

Ok here is what I got .I did just like you asked black lead on the chassis for ground and on V5 pin number 3 493 dc volts pin number 4 494 dc volts and pin number 5 negative -56.3 dc volts . On V 4 pin number 3 495 dc volts, on pin number 4 492 dc volts and on pin number 5 negative - 56.3 dc volts. ( no power tubes in and in play mode these test were done )

[danman]

All of the numbers look good. I do wonder why pin 4 on v5 reads slightly higher than pin 3. Does your amp have a screen grid resistor installed and tied to pin 4 on each power tube socket? Most of the time pin 4 will read a few volts lower than pin 3 because of the voltage drop across the screen resistor. You don't seem to have a major difference so I do not believe that it is causing you any issues though. You seem to have proper voltages on the filament circuit and at the power tube sockets so I would take a good look at the preamp wiring, especially the input jacks. Also doublecheck your wiring of the impedence selector and output jacks. Could you post some new pictures of these area now that you have cleaned up some of the wiring? We may be able to spot a problem that you may have overlooked.

You asked earlier if anyone had completed one of these Tubedepot JTM45 kits. I remember reading awhile back that a couple of members over in the "marshallforum" had built the kit and were very happy with the amp. Keep plugging away at it and you will find the problem. Do you possibly have any techs in your area that could take a look at the amp and help you find the issue?

[danman]

I forgot to ask earlier, does the fuse hold when you power up the amp into play mode with the power tubes installed? What happens with the tubes installed? Is the amp silent, does it make any sound at all? Be sure to have a speaker connected when doing this though.

[fixer2]

Yes I always have a speaker hooked up and the fuse is fine ,but there is no sound at all not even a hiss when I turn up the vol.controls all three even the master all the way up too , nothing at all.I know my reserch before I got the kitmakes me really to get it going it has some neat mods to the jtm 45 designand the price was alright,.At the time I did not know of metro or evem mojo amp kits ,but I did like the build and want to do a jmp style or a jcm 800 50 watter .I will get the pictures up and first do some more checking so maybe I can have some more info too to ask.

[danman]

When you were checking for voltage at the power tube sockets, did you hear a pop through the speakers when you touched the red probe to the pins? You will normally hear a small pop everytime you touch the socket pins, especially pin 3. If you are not hearing this then I would suggest taking a good look at the OT wiring, imedence selector and output jack.

[fixer2]

I was started into looking at the wiring at the OT ,and I thought review the instructions while I do this and see if I put something in wrong.and then I thought why not compare tube depot instructions to Metro instructions.I saw that Metro hooks up a resistor on V4 and V5 pin 4 and pin 6,Tube depot hooks up a resistor on pin 4 and pin 5.Is this because the differnt tubes Ktt 66 vs EL 34. Iam going to make a singal tester to generate a sound out of a old tape player into the inputs and trace around until I find where the singal stops, I will do this after I go threw very very well the OT wire hooking up to the speaker selector and out put jacks etc.May be something is over heated who knows this is really a stumper

[fixer2]

Oyeah I do get a little crackling when I put the test probe on the tube pins

[fixer2]

Looks like my question on the resistor on the pins is the differnce of the two tubes ,and so far the tester I wanted to make from gerald webers book tube talk I cant find the parts that capcitor he said to use.but I will keep looking at my wires and get you the pictures

[danman]

What value resistor did you use at pin 5? Pin 6 is an unconnected pin so Marshall always used this to hold the 1k screen grid resistor that attached to pin 4. I do not know if the Tube Depot kit uses a screen resistor (it should) so it may be using pin 6 to hold the control grid resistor that attaches to pin 5. Marshall amps have the control grid resistor (usually 5.6k) tied directly to pin 5 because pin 6 is used for the 1k screen grid. Either way, just be sure to follow the Tube Depot instructions for now until you get the amp up and running right. There layout is different from most others so you cannot compare it to the Metroamp layout.

You never did mention whether or not you heard a "pop" sound through your speaker when you were taking voltage readings. This is a great way to troubleshoot each stage of your amp to find out where the signal stops at. On the preamp tubes, touching pins 1 or 6 with the amp powered up (tubes installed) and the standby switch in playing mode, you should hear a definite pop through the speaker. For the power tubes, touching pin 3 with your meter lead should produce a pop. Work your way backwards from the power tubes to the preamp tubes and let me know if you hear it.

[fixer2]

Ok this is what I get V1 pin 1 & 6 nothing no sound nd it is in play mode all controls at half way.V2 yes and little crackly sound but not really loud,V 3 loud crackly sound V4 nothing V5 yes good crackly sound. The other day someone e-mailed me a picture of the inside of their working tube depot jtm 45 plus build I see they ran the master vol. mod from a differnt piont but I did mine just like the instructions I got with the kit.I did notice a resistor in a differnt place then on mine were the resistor is linked with a acp. but maybe this will feed the cap differnt but I will move it over from one side of a jumper wire to the cap to the other side of the jumper wire I will tell you how this works out I first have to bleed off the voltage in the big caps before I re-soilder.

[danman]

Did have all of the tubes installed when you were checking this? Since you do not hear any noise through the speaker when probing the plates of v1, doublecheck your wiring carefully. Each channels AC signal voltage should leave the plates of v1 (pins 1 and 6) and travel through the .022uf capacitors and then on to the volume pot for each channel. From the volume pots the signal comes together at the two 270k mixer resistors and then on to the grid of v2 (pin 2). Check your wiring closely in this area and make sure that you have the volume pots wired correctly and properly grounded. It may help to look at a standard Marshall style layout for your amp to help you trace out the signal path.

When you were probing pins 1 and 6 of v1, do you happen to remember what your DC voltages were reading?

[fixer2]

All tubes where in but I will go back and get the voltage amount you asked for Thanks

[fixer2]

I move the resistor from t 12 to t14 like the picture someone e-mailed me of there tube depot kit build and I dont get as much crackly sound on v2 pin 1 but what I get is 181 dc volts on pin 1 on V2.And on V1 pin 1 I get a negtive dc voltage of .76 .I see in a drawind lay out I found online that the two resistors ce together on t12 and the cap goes to t 14 and there is a jumper wire going from t12 to t14 and there is a wire hooked up to t12 going top pin 2 on V2.so I will try this after I bleed ihe voltage off again ( to be safe )

[danman]

If you are reading a negative voltage at pin 1 of v1 then you must not have your B+ wiring correct. The two 100k plate resistors that are joined together on one end and then go to pins 1 and 6 of v1 should have DC voltage between 100-200vdc. Make sure that you have the board jumper wiring correct that carries the B+ to the turret on the board where the two 100k resistors meet. Without proper voltage at this junction the v1 tube cannot amplify signal. It is really easy to trace your B+ down the board. Just follow the board jumper wires that connect to the 10k dropping resistors for the preamp. You should see DC voltage at each 10k resistor and make sure that the jumper wires that connect to the plates of each preamp tube are routed properly and soldered correctly.