Ceriatone Forum

 Hello  and thanks,Im new to this forum,Im building a Lightning from left over parts,Id like to know bias, screen and plate voltages from Nics build, or just as well the DC @ pins 8/2 using his transformer.the Hammond power trans I have supplies 327AC  @ pins 7/8 and 410 DC @ pins 8/2. my build will obviously will need some voltage mods . I see that the Ceriatone schematic indicates 290V@pins 7/2.that would provide  a much lower B+ than Im getting from the hammond.  any help much appreciated, Thanks Pat

If anyone has these ...then I'd love that info myself as I'm nearly completion of my lightning build... getting ready to power it on tonight.!

Cheers from Scotland!

Stuart

Open the link " Voltage chart" at bottom left of this link
http://www.ceriatone.com/tlbrBorderSub/link.htm

This should be a sticky

Todd

Thank you so much ... this is a big help :)

Well I certainly have some differences in my voltages at these test points. I'm using 240V obviously which is what the spreadsheet has as input voltage.

I'm using the ceriatone schematic and getting the components etc myself.

Looks like I have some debugging/fault finding to do.

Stuart

How different?
The spreadsheet is kind of a ballpark comparison.
If there is only a 10-15% difference it may not be an issue depending on where the readings differ.
Post your readings if possible.

Todd

Todd

I'll post my readings tonight...

It looks like I have an issue with my driver/phase invertor tube (tube 3)  ...  one of  the two 100K resistors that feed onto pins 1 and 6 are failing.  I replaced them by 1W resistors as I was worried half watts would not be good enough, but still pin 6 resistor reads very low/fails. My valve amp guru is in hospital so I dont really have anyone to turn to!  So hope you guys can help me :)

Cheers

Stuart

Stuart

Readings from my amp (in brackets)

Tube   Type   Pin1   Pin2   Pin3   Pin4   Pin5   Pin6   Pin7   Pin8   Pin9
                              
V1   12AX7   149 (73)      1.4 (1.56)         149 (73)      1.4 (1.56)   
                              
V2   12AX7   191 (148)      1.5         317 (298)   191 (149)   192 (152)   
                              
V3   12AX7   237 (172)      65 (62)         242 (172)      65 (62)   
                              
V4   EL84         12 (11)            335 (325)      340 (326)
                              
V5   EL84         12 (11)            335 (326)      340 (320)
                              
V6   GZ34            281 (237)      281 (238)         
                              
OT CT   340   

I looked at the V1 pins 1 and 6 as this obviously well out and I noticed I have an incorrect capacitor that feeds pin 1 it should be a .0015uF and I have a 0.000015 would that make that voltage difference? I ordered the wrong caps... so have put in an order for the correct ones.

I guess this might have a knock on effect on the rest of the pre-amp circuit?

Does it explain why I get no guitar sound at all from my amp?  all I get is a hum... which increases in volume as I increase volume and master pots?  I suspecta grounding issue or perhaps output transformer not wired correctly?

Any help would be very welcome!

Thanks

Stuart....

                        

The cap being wrong size should not be the cause of the readings but you should get the right size in there
Make sure and check all your ground connections are in place.
If possible post some gut shots

Todd

Todd

I found one fault on the input jacks that is causing the guitar signal to go to ground! Poor soldering.  I have ordered the correct Capacitors.  They should arrive tomorrow. I'll re-solder the input jacks.  I am now getting some guitar ... but at low volume. At least this is a step forward !

Doesnt explain my issue with the low voltage though as there seems to be plenty voltage before the 200K resistor immediately before pin1 on Tube 1. and the resistor seems to be OK.  it is only .5W maybe a need a 1W resistor there?

Cheers

Stuart

Hey Stuart

Good find on the input jack. The wattage of the resistor will not be the problem. If it was underated the resistor will turn black and the smoke will come out :o
Maybe just double... triple.. check every connection and component value again. theres probably something off

Todd

Todd

Already started on re-doing the wiring.  Should complete that today.  This is my first real amp build. I'm using this a prototype to work out best location of valves , components etc. So I see this as all part of my learning.

The frustrating part is getting mu soldering skills to a high enough standard that I am happy with it.

:)

replaced the capacitor and 221K resistor (the original spec was for 220k) with a 220 K resistor... still only getting 74V after the resistor instead of 149  but the voltage I'm getting before the resistor is 274v maybe the jumper wire from the filter capacitor is the issue? ... the hunt continues..

Hey Stuart

Is it possible to take some gut shots and post them here?
Also I would check all the dropping resistor values are correct. They are the large resistors mounted next to the larger electrolytic caps. Meter for continuity across the underboard jumper wires to make sure they are in correctly.

Todd

Todd

I found the problem with the voltage. I was the jumper wire from the filter cap to the 220K resistor.  It was either soldered badly(likely) or the wire was not up to the job current wise.  ANyway I now have 149V at this point!

I still have an issue with getting any decent volume out of the amp.  I think this is again to do with bad wiring round the input jack area, because if I wiggle the guitar jack in the socket I briefly get some good volume.

I am going to re-do my wiring in this are and replace all the tone and volume pot wiring with upgraded wire.

I will post a gut shot, but I'm nervous about it as my wiring is very poor, I will take some pics at the weekend.

Appreciate your advice so far Todd, its been a big help.

 

Stuart,

Good find on the bad wire! Did you check all your voltages again on all the tubes? Hopefully they are all now in range.
No worries on the poor wiring job, we all start somewhere.
Sounds like you are getting pretty close to having a working amp
Todd