I've made a start :) 50w #102

[aflynt]

on the original talbany 102 layout the capacitor at the top of the pre amp board from the presence control into the phase invertor circuit is show as a 2.2uF orange drop but on other layouts it's shown as an electrolytic, can I use a 2.2uF orange drop 600PS as I don't have an electrolytic to hand?

also can I use a 100k( or 120) instead of a 110k resistor on the 10k P.I trim pot?

Marcus

I believe it's meant to be a Tantalum cap. In the #102 gutshot it looks like a blue radial electrolytic to me. I'd recommend finding a 110k for the PI so you have enough range to set the trimmer.

-Aaron

[martin manning]

You can use any kind of cap for the 2.2uF: film, tantalum, or aluminum electrolytic. Not much voltage there either, so a low-voltage cap is fine. There might be some subtle difference in sound, but anything will get it working.

I'd get those PI plate resistors right, 110k and 120k, or at least keep the difference at 10k. Otherwise you might not have enough range on the 10k trimmer to balance the PI.

[norburybrook]

Thanks again chaps the hand holding is appreciated. I've ordered some Tntalum caps and 110 k resistors.


Good thing about having to wait for these parts meant I was checking my board against a few gut shots and realised I'd mixed up 0.1uF and 0.001uf caps due to my printout not been that clear.... will try and work from my tablet now which has a very clear high res screen.


OK new question;

I don't won't to use the jazz/rock switch as I've never found it useful, so how do I wire it without? Specifically regarding the relay as it seems to connect either side of the resistor. I didn't think the jazz/rock had anything to do with any switching outside the front toggle.

TIA



Marcus

[martin manning]

It'd be easier to leave the R/J in, wouldn't it? What will you put in its place?

[norburybrook]

Nothing .

My chassis and faceplate aren't cut out for it as it came from a friend who never used the jazz/rock thing either, otherwise I'd have put it on for ease of layout following as you say.


Marcus

[10thTx]

I don't won't to use the jazz/rock switch as I've never found it useful, so how do I wire it without?

Not sure if this is what you are looking for, but I'll offer it for consideration.

with respect, 10thtx

[norburybrook]

thanks 10thtx, that's probably exactly what I need

I just need to work out which connections are which as regards to the relay board/schematic.


Relays are a whole new ball game for me!


Marcus

[10thTx]

Maybe this would be useful? There is a ton of information here about relays with photos, schematics and layouts:

http://el34world.com/Forum/index.php?topic=14348.0

and more here:

http://el34world.com/projects/relay_switch.htm

with respect, 10thtx

[martin manning]

Marcus that scheme is not what you want. ODS 102 has a PAB like 124, and the deep switch is mid boost. I'll mark up the layout later today.

[norburybrook]

Marcus that scheme is not what you want. ODS 102 has a PAB like 124, and the deep switch is mid boost. I'll mark up the layout later today.

Thanks Martin , the learning curve steepens.......



Marcus

[bluesfendermanblues]

A lot of us have build the original designs and found the sound of the #124/102 PAB to be rather strange, with a lot of high treble and a lot of muddy bass.

I guess you have to hear it yourself in order to make your own judgement, but I would recommend lifting the bass pot (10k resistor end to ground) and the mid pot....

Some like individual resistors on each pot and some like to tie the ends together (10k pot on bass pot and ground log on mid pot) and lift them with one resistor.

For individual values you could try 100k on the mid pot and 220k on the bass.

If you tie them together you could try 180k to ground - or your could even go for 22m 'Mega boost' and get the Bluesmaster/Marshall sounds in OD+PAB mode.

Personally, I like the "100k on mid / 220K on bass" version.

[martin manning]

All Rock and no Jazz.

[norburybrook]

Thanks Martin, that's perfect, I'm sure it will be useful to others as well in the future.


Couple more observation/questions, I beginning to see this layout in my dreams now.....

Some layouts have a 120R resistor to ground from the heater wires on the output valves, well just one valve, what are they for?

Grid stoppers; I've seen these wired across the valve or in line , I presume this is just a personal choice?

Does the voltage regulator for the relay boards need to be screwed down to the chassis to act as a heat sink? I know they can get very hot.

Last question; I've used Piher carbon resistors on my cathodes is this bad, should I use metal film instead?now's the time to change them.

Thanks

Marcus

[martin manning]

Some layouts have a 120R resistor to ground from the heater wires on the output valves, well just one valve, what are they for?

You should see one from a pin 2 and one from a pin 7. They form an artificial center tap for the filament circuit. If your PT has a physical CT, you don't need them, but you need one or the other to prevent hum.

Grid stoppers; I've seen these wired across the valve or in line , I presume this is just a personal choice?

Fender used pin 1 as a tie point for the grid stoppers on 6L6 and 6V6 because there is no internal connection to that pin in those tubes. If you want to try EL34's at some point, then you have to tie the suppressor grid (pin 1) to the cathode (pin 8), and then to ground (through a 1R current sense resistor). If you want the option to use EL34's, then tie pin 8 to pin 1 and do the grid stoppers in-line, Marshall-style.

Does the voltage regulator for the relay boards need to be screwed down to the chassis to act as a heat sink? I know they can get very hot.

I haven't run the numbers on it, but yes I'd just bolt the regulator to the chassis as shown in the layouts.

Last question; I've used Piher carbon resistors on my cathodes is this bad, should I use metal film instead?now's the time to change them.

HAD seemed to use 1% tolerance MF resistors for both plates and cathodes, presumably for low noise and precision. The plate resistors are more significant with respect to noise, so if your CF cathode resistors are 5% or better I think you are fine.

[norburybrook]

thanks Martin,

I've got some 120R 1 watt metal films would they be OK and would a 1R carbon film 1 watt do ? I realise the talbany 102 layout I've got doesn't specify resistor wattages apart from 'yellow resistors all Sprague Q line CF'

obviously the output tubes are carrying higher power than the preamp board so best to check what's what.


I'm going to have to do another mouser order to get my footswitch parts so I can add to that if needs be.


I seem to have ordered lots of stuff I don't need and have missed bits I do


Marcus