Help with a master volume 100 watt kit using kt-88

[kydu0]

I purchased a head that was wired to a schematic that was here on this forum somewhere...and i cant find it anywhere..It is a two power tube kt-88 amp,and has3 preamp tubes...it was wired incorrectly and has many issues that i would like to solve..if anyone has info on this schematc or amp ..I would be very appreciative...thanks
-Kydu0

[spaceace76]

any pictures? can you draw a schematic of it and post it here? that would make it much easier to help you. also, all schematics are available in the wiki, which you can access from the top of this page. no metro kit comes stock with KT88's, let alone 2 KT88's at 100w. i urge you to use the search function if you haven't already.

[kydu0]

This is a modified Marshall JTM 45 circuit with a master volume and JTM45 cascading gain "one-wire" mod. The master volume is between the tone control and the cap to the phase inverter. Go to the supplied short cut. The Master volume is between VR3 and C8. On the front end, one channel of input jacks is removed and pin 2 on V1A is connected to pin 7 of V1B. This is some times called a one wire mod.

http://forum.metroamp.com/download/file.php?id=9935" onclick="window.open(this.href);return false;

That is what the guy sent me...i cant get any info opn it

[demonufo]

One thing that needs mentioning is that there is absolutely no way on earth that any standard 2XKT88 marshall style amp is going to be rated at anywhere near 100W using a standard PT from either a JTM45 or a 50watter. Biasing KT88's for 100W at idle will strain the heck out of the PT, and it will sag like crazy. If you have a very high B+ it will help, but the limited current will still be a major issue.

[kydu0]

I am aware of this..this is what the guy sent me for info..he said the schematic was here...in my previous post there was a link to the sdupposed schematic at this sight..that all i need to fix this thing...thanks for any input...

[gldtp99]

The schematic link says "the attachment no longer exists"----- how we could help is if we could see good pics of the circuit, transformers----- then we could see exactly what your amp consists of as far as circuit mods and what PT/OT you've got-----you say that it's wired incorrectly and has many issues you'd like to fix---- and it's a JTM45 circuit with a one-wire mod and added pre-PI MV.
Getting the amp into whatever configuration you'd like it to be doesn't seem to be all that hard ------ do you want a stock JTM45 circuit ? Or do you want a cascading preamp with a pre-PI MV circuit that works properly ? The question of type of output tubes will depend on what transformers are in the amp now, and what type of overall tone you're looking for---- i don't always use the usual "Right" output tubes in all amps---- my Marshall JTM45 RI that i've modded to be more like an orig JTM 45 runs Sylvania 6L6GC's instead of the "Approved" KT66's--- this amp sounds terriffic------i built a 50 watt Slash-type #36 Mod amp that uses 6L6GC x 2 instead of KT88 or EL34 (amp kicks ass)----- i've built Blackface Fender-type amps with KT88 x 2 (@75 watts) with transformers matched to the requirements------- the owners like them very much----i usually build Marshall 50/100 watters with EL34's and larger Fender-types with 6L6GC's but i've built JCM 800-based amps with EL84, 6V6, 7868, 6L6GC, EL34, and KT88 output tubes---- people like all of them---- matching PT specs, output tube specs, and OT specs is important----just randomly installing non-standard output tubes isn't the right way to do it and usually won't give good results.
So getting the circuit sorted out to however you want the amp to sound is Job #1------ deciding which output tubes to use is secondary (if KT88's are a reasonable choice or not depends on the transformers, not so much the type of circuit-- and also just what type of amp tone you're looking for).
Post some good pics and you'll get plenty of responses, i"m sure................gldtp99