5150 mods... revealed w/ pictures

Hi guys, sorry to dig up an old thread, but I'm going to try some of these mods out and I had a couple of questions.

1. The only capacitors I could get at Radio Shack are rated for 50V. Is this too low to safely run for the V5B hack? Would the choice of 6/7 or 7/8 affect the voltage rating I need?

2. My 6505 is the 2x12 combo, and I've noticed a few minor differences compared to the head. Specifically, C26 on the head doesn't seem to exist in mine. According to the head schematic, C26 comes out of V1B, pin 3, in parallel with R17 and C4. The combo schematic (and I checked to see that my amp matches it) only has R17 and C4 (numbered differently for the combo, of course). Would this mean that the C26 mod is essentially already included with the stock combo?

Edit:

Since I had the amp open anyway, I threw in the R9 mod and bypassed C15. Just those made a pretty big difference - without a boost of any sort, cranking the Lead Pre just gets me to the right place for a metal tone, and there's pretty much no noise when I'm not playing. The Rhythm channel is actually useable as a clean or a rock crunch now, and with my Tubescreamer everything is gravy. On top of all that, the amp feels like it's responding a lot quicker when I play - previously, without cranking the gain, trying to play anything heavy sounded like the notes were being really lazy on their way through the amp.

I'll have to set up my EQ in the loop again, since the high frequencies are being emphasized differently, but overall I'm pretty happy with the change.

droptrd":2u353phn said:

I tried R9 all the way up to 350K. I liked it better around 300K. But in the end I took the mod out completely. I made the mistake of A/Bing it with my Tverb. The 5150 sounded like an AM radio by comparison. I also took out the 10pf mod too, for 2 seconds and then put it back in. That ones the keeper for me. Still want to do the bias mod though.

Ran the 5150 and the Tverb together today also.........Warning, may evaporate small children and animals Finally found a good use for the Tverbs scoopy Red/Modern gain ch Paired great with mid heavy peavey

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I run my 2 channel recto and 6505+ togethor and it is bliss ...

what happened to the pics in this thread?
all this yapping made for a really long and uneasy read after coming back to visit this.
some simple, easy to follow pictures would solve the problem.

anyone??

Neeklaus":rmwm7i9t said:

what happened to the pics in this thread?
all this yapping made for a really long and uneasy read after coming back to visit this.
some simple, easy to follow pictures would solve the problem.

anyone??

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long story but the original poster of this thread asked that his account be deleted or whatever, and with it went the posts/pictures he made. not sure if it was actually deleted but i do know all his posts and stuff are gone

psychodave left, and a lot of his pics and youtube stuff was removed, IIRC.

what mods are you looking for?

I suppose all the mods explained in this thread by the now removed posts

no
just daves posts got removed, which, unfortunately, were the ones containing the pics and vids, which, if i understand it, is what happens when you ask for your profile to be deleted. i had emailed him about this very thing to try to glean some info from him back in march, but heard nothing back. bummer, i really liked his posts and his info that he put forth for us.

DUDE":nh02qvod said:

V5B(middle preamp tube add 10pf silver mica cap to pins 7 and 8. This is the main mod!!!
R9: piggyback a resistor on top of the 1 meg resistor. I used a 120k based on feel. You can try out 68k, 100k, 120k, 150k, etc. This tightened up the map a lot!
C26: cut one leg for less bottom end on the rhythm channel
C15: bypass cap for better "feel"

I tried tinkering with R15 and using Marshall vlaues, but it took too much away from the original sound. The 39k is the SLO value as well.

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Trying to figure out where the pin numbering begins looking at the tube sockets?
Also, I have two 5pf mica caps, I can either parallel them to pins 6/7. Or run one from 6/7, the other to 7/8.

pin numbering is left to right looking at the bottom of the board...meaning the tubes are on the other side.

i actually put 10pf on 6/7 and 10pf on 7/8 at first, both switchable via dpdp on/on switches. i noticed more difference on 6/7, so, i connected both switches to 6/7, one with 10pf, one with 2 10pfs paralell...that way, if i wanted more high cut, i could turn them both on, and have 30pf in parallel. personally, the 6/7 pin 10pf mod isn't really worth it if you have a useable presence knob in this amp...that's a whole nother animal though that i haven't figured out. so for now, i have the 6/7 pins as stated above. 5pf by itself might not be enough "cut"...but 2 5pfs in parallel, yes, would be 10pf, noticable when hardwired, but REALLY you can tell the difference when put on a switch. just depends if you wanna drill holes in your amp. i didnt care, so i went ahead and did it that way.

Could anybody post a picture showing where C15 is?
sorry to bring back an old thread, i just have no idea where to find that cap on the board

Okay i know it's an old thread, and i am quite accustomed to the forum user's creed, but i only just found this thread and it looks great

i have some questions though......

Why is the cap in the mod 10pF? how do other larger/smaller values work? could i use say a 47pF and a 10pF in series (8.25pF) to similar effect? am i right in saying that higher value = darker amp and less noise? what are the boundaries?

also, as to the whole R9 malarkey, can i instead of a set resistor value use say a 68K and a 250K pot in series to have a set range of values, but they can be variable? so i can change the setting on the fly hopefully

so, i am thinking that if i supposed correctly with the above, i should get all this going on sooner or later:

sell family to afford mods,
5751 JAN Phillips in V1,
R9 variable (68K-318K),
Mercury Magnetics choke,
Bias mod,
8.25pF silver mica setup on V5B pins 7/8,
TAD 6L6GC-STR power tubes,
upgrade screen grid resistors,
make loadsa dough by being a huge big time rockstar with an awesome amp,
buy family back (obviously ask for a receipt though..... just in case).

how does all that sound for a setup? tight as nun and heavy as Whitney Houston's drug use methinks

jcj":1d970jwq said:

psychodave":1d970jwq said:

I spoke to Mark Cameron tonight and he said it was okay to reveal the mods he gave me for the 5150.... so here is what has been done to my amp:

V5B(middle preamp tube add 10pf silver mica cap to pins 7 and 8. This is the main mod!!!
R9: piggyback a resistor on top of the 1 meg resistor. I used a 120k based on feel. You can try out 68k, 100k, 120k, 150k, etc. This tightened up the map a lot!
C26: cut one leg for less bottom end on the rhythm channel
C15: bypass cap for better "feel"

I tried tinkering with R15 and using Marshall vlaues, but it took too much away from the original sound. The 39k is the SLO value as well.

There you have it. Have fun getting a killer 5150 sound

Thanks Mark!!

(Please note that JerryP gave me some other ideas, but I didnt use them and I wont reveal )

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Hanging out with Mark makes wish I knew more about working on amps... I can barely change a guitar string Totally wasted on me

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I realize this is an old post so..... here goes anyway for others to read who share our interest.

This is my first post here. I do not wish it to be negative, however. I completed the 10pf to V5 of a 1991 5150 and found it to be less inspiring than the stock circuit. I own a Cameron modded Marshall 2204 and have built a few amps.

I will go slowly into making changes to this 5150 circuit as it is I believe a first year production. Think I will look at adding some mids and try to smooth out the fizz a bit. Not really a problem when mixed live with bass and drums but playing alone there is room for improvement.

Respectfully, New Religion ♫

I have played a bunch of modded 5150s... They sound and feel best stock IMO, all you need are tubes that sound best to you and at the very most a bias mod but thats not really needed either. They kick ass stock

Sorry to sound amateurish.. What do you mean when you say bypass? Referring to C15 specifically.

To remove it?

NewReligion":2bgut1cx said:

This is my first post here. I do not wish it to be negative, however. I completed the 10pf to V5 of a 1991 5150 and found it to be less inspiring than the stock circuit. I own a Cameron modded Marshall 2204 and have built a few amps.

I will go slowly into making changes to this 5150 circuit as it is I believe a first year production. Think I will look at adding some mids and try to smooth out the fizz a bit. Not really a problem when mixed live with bass and drums but playing alone there is room for improvement.

Respectfully, New Religion ♫

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Hi David, great to see you on the forum.

Oh man! I forgot about this thread... Makes me want to pick up a 4th 5150 and mod the hell out of it!

one of the best mods i've done so far to my 5150 was install a dpdt switch for half power.

its wired to break the grounds on the last two output tubes (v8/v9).

people are going to say it's only a 3db drop in volume. i will say back, it's more significant than that marginalization sounds. it's a BIG volume drop. perfect for club gigs. it took me about 10 mins to install and wire.

schematic for a mesa 2b pretty much maps it out, the area in the red:



my next mod will be a pentode wiring switch, and a power scaling, but not the standard scaling most guys think of. more of a signal limiting of what goes into the output tubes from the phase inverter like the marshall TSL has, but more detailed (for more settings and versatility).

my amp has a lotta mods done to it, and i love them all.

Necro bump..... Does anyone have the pics from psychodave saved they could share with me?

Thankfully his posts were quoted so they weren't deleted but his pics were.

Come on I know one of you has these pics saved!

bump! whos got the pics!?

i had a sweet 3 channel jerryp modded 5150 once, that totally KILLED, but i eventually sold it once i got the Boogie mark series bug, which i still never recovered from.