poison7512
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- Aug 12, 2012
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Hi there!
I have a stiletto Ace head that I have modified twice.
First mod I added a 100pf cap to treble pot, changed R44 to 5.6M, and added a three way on/on/on switch to switch between mid slope resistors (R38 - 33k, 39k, 47k) Amp worked perfectly and sounded great!
I was still not totally happy and decided to take it a step further
Second mod I added a switch to switch out caps on treble pot (on/off/on 100pf, 220pf), switch to switch R44 values (on/on/on 5.6M, 3M, 1.5M) and a pot off resistor R83 (bias pot was 39k now 33k - 43k [33k +10K pot]) and I also installed a JJ GZ34 rect. tube
Im very careful and somewhat experienced in electronic repair and after the success of the first mod I figured this would go very smoothly.
I set the bias pot for the stock value (39k) and plugged in and turned on and with the effects loop bypassed the amp sounds wonderful...
However now after the mod (my work is very clean and thorough) when the Loop is engaged I get a horrible loud hum through the amp that was never there before! perfect when bypassed but an awful hum when the loop is IN. The send knob on the back has no effect on the hum volume, but the ouput knob on the front seems to take away the hum as you turn it up, like all the way up to unusable levels. You can hear the noise floor being raised from all the gain by turning the knob up like normal, but the awful loud hum fades away as the knob (output on the front) is turned up.
I know about the problems with V4 in this amp as that tube is a cathode follower (im using all JJ gold pin 12ax7) so I tried replacing V4 and that did not solve the problem (I even changed out V3 and V5 but obviously that didnt help)
I then reversed all the mods but the problem persists, is it possible to have heated up a nearby resistor when soldering causing it to lose its value? I have the schematics and the effects loop seems like a simple enough circuit I just unfortunately lack the experience and knowledge that Im sure some of you posess, especially Charles Reeder and the member Isaac who posted here about the mods which were great ideas.
has anyone had this problem and successfully diagnosed or repiared it???
any suggestions as to how I should go about diagnosing and repairing this myself?
The local mesa service guy does decent work but takes FOREVER and is expensive!!! , obviously there is no warranty because the amp is modded even though the mod were very basic.
Id just use my lonestar but I have a failing relay (its been an unlucky month for me in amplification) and the part my not come in in time. I have gigs this week and really need to use the Stiletto and have a functioning effects loop
Could someone please help point me in the right direction? I promise you will earn much KARMA
I have a stiletto Ace head that I have modified twice.
First mod I added a 100pf cap to treble pot, changed R44 to 5.6M, and added a three way on/on/on switch to switch between mid slope resistors (R38 - 33k, 39k, 47k) Amp worked perfectly and sounded great!
I was still not totally happy and decided to take it a step further
Second mod I added a switch to switch out caps on treble pot (on/off/on 100pf, 220pf), switch to switch R44 values (on/on/on 5.6M, 3M, 1.5M) and a pot off resistor R83 (bias pot was 39k now 33k - 43k [33k +10K pot]) and I also installed a JJ GZ34 rect. tube
Im very careful and somewhat experienced in electronic repair and after the success of the first mod I figured this would go very smoothly.
I set the bias pot for the stock value (39k) and plugged in and turned on and with the effects loop bypassed the amp sounds wonderful...
However now after the mod (my work is very clean and thorough) when the Loop is engaged I get a horrible loud hum through the amp that was never there before! perfect when bypassed but an awful hum when the loop is IN. The send knob on the back has no effect on the hum volume, but the ouput knob on the front seems to take away the hum as you turn it up, like all the way up to unusable levels. You can hear the noise floor being raised from all the gain by turning the knob up like normal, but the awful loud hum fades away as the knob (output on the front) is turned up.
I know about the problems with V4 in this amp as that tube is a cathode follower (im using all JJ gold pin 12ax7) so I tried replacing V4 and that did not solve the problem (I even changed out V3 and V5 but obviously that didnt help)
I then reversed all the mods but the problem persists, is it possible to have heated up a nearby resistor when soldering causing it to lose its value? I have the schematics and the effects loop seems like a simple enough circuit I just unfortunately lack the experience and knowledge that Im sure some of you posess, especially Charles Reeder and the member Isaac who posted here about the mods which were great ideas.
has anyone had this problem and successfully diagnosed or repiared it???
any suggestions as to how I should go about diagnosing and repairing this myself?
The local mesa service guy does decent work but takes FOREVER and is expensive!!! , obviously there is no warranty because the amp is modded even though the mod were very basic.
Id just use my lonestar but I have a failing relay (its been an unlucky month for me in amplification) and the part my not come in in time. I have gigs this week and really need to use the Stiletto and have a functioning effects loop
Could someone please help point me in the right direction? I promise you will earn much KARMA
