Imbesi Guitar Repair and Amp Repair

08/20/2024

02/24/2023

Vibration: the second most damaging situation to a guitar amplifier whether it be solid state or tubes. I know it's very convenient to place an amp head on to the cab u play out of but the louder u play the more the cab vibrates and over time the components subjected to this will come loose from the solder holding them to the carrier and component lead failure or intermittent conditions take place resulting in bad tone, distortion and sound drop out or ground reference failure in the preamp. Besides heat being the number one problem, vibrations are second. After 5 years of vibration most guitar and bass amps will develop minor to major issues. To minimize this effect move the head to a tv tray not near the cab, usually there's no room to do something like that so the next best thing to do is place a 2" thick piece of foam between the cab and head. Nothing can be done about a combo amp except to install a fan to cool the tubes or solid-state heat sink inside the combo case to at least get rid of heat.

Keep all Amplifiers a few inches away from a back wall when in use. If air gets trapped in the cab with electronics more heat is trapped as well shortening tube or transistor life. All electronics generates and is around 20 degrees hotter inside the chassis then the outside air so if it's 80 degrees outside it's around 100 degrees inside the chassis or can be more. Consumer electronics begin to degrade around 130 F degrees. Military grade much higher but your amp is only consumer grade unless stated by the maker. Finally if u are not going to use your amp for more than 15 minutes, shut it OFF, Not STANDBY. No all but many tube amps in Standby mode is still charging the supply caps, over charging can occur in time and shorten life to only a few years. Cheap caps can go in 7 years to 10 years that way. More expensive caps should lst 2 to 3 times longer. If the caps are failing u will hear more hum than usual when all pots are turned all the way down. There are other signs but visual inspection of the caps themselves are necessary. Also a defective Rectifier tube can cause hum, blow fuses, bad audio tubes can cause hum also. I hope this helps those taking the time to read.
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09/17/2022

Getting closer to the time of turning on the new single channel 30 watt i
named after my oldest daughter Christina Marie. I have to tune the Slope control which alters the tone tank. Most amps do not have this option at all. More later about other features.....

09/02/2022

Hi Everyone my third amp creation, the CM 30 is one channel, reverb with Dwell control, tone tank Slope control to change the way the tone tank treats the Middle Range tone shift, 30 watts from 4×6V6GT POWER TUBES, between 25 and 35 watts. Not sure yet if the power amp will be Class AB1 or Class AB. AB1 uses 5 to 10 watt cathode resistors to regulate how much current is drawn and AB uses a minus bias supply to control the power tubes. I'll get more power with AB but AB1 GIVES U WARMER TONE and less power. I have to try both versions before I decide which way to go. These amps I build ARE NOT COPIES of anything on the market. They can sound like iconic amps but they have their own sound also. I nay include a switch that changes the reverb into a clean boost. Not sure yet......

05/01/2022

this a final version of the ME 45 watt hand wired channel switcher with loop all tube audio path with meter jacks in the back for setting the bias. no "bias king" needed. 4, 8 and 16 ohm matching, effects loop has series /parallel mode, can be used as a boost, power tubes can be 6L6, EL34, E34L, KT66, KT77 and probably KT88 AND 6550. the amp will roughly put out the same amount of power regardless of tube configuration, just sonic differences. this amp has its own dedicated bias transformer and supply unlike most other amps. i have not tested the last 2 type power tubes yet in the power amp. one of each can be used also. I'll include a biasing chart for tube use. the preamp tubes are 12ax7 or similar, a 12AT7 can be used in the phase inverter socket, l prefer that sound but it can be a 12AX7 or similar. Any questions text or call.

02/25/2022

well, it looks like im building two different amps. one is around 50 watts the other 30watts. different power tubes so they sound different from each other. preamp controls and features are the same. redesigning the face and rear plates for corrections that were made. i gotta talk to dean gate wood about building some cabs for me.... these are in between the iconic tones out there.

12/11/2021

Finally! a circuit design that's stable, quiet, loud in both channels with tone controls overdrive and clean, a tube drive and recovery effects loop with gain controls, can run around 6 different type power tubes mixed and or matched or not. separate dedicated bias circuit for power amp and switcher, led indicators. the loop can drive another power amp. i will have chassis #4 into a head case or combo cab before Christmas to demo! then i'll rebuild #3 chassis . that one has 4xEL84 tubes in the power section and the same preamp and loop. chassis #2 and #1 are probably not rebuildable. they are all proto types

12/05/2021

well after much figuring and experimentation i got a way of fitting the channel switching circuits into the small chassis box i had 10 made at the cost of 1000.00 dollars. i have the 1st one almost completely done and about to test. i should not have to do much testing because i already voiced the preamps and documented that info in previous versions. i have 2 other chassis built so as soon as this first one is done which is a head cab version i can rebuild the boards in the other 2 and have 3 available in combo cabs. at this point i have 2 new empty head cabs a combo 1×12 cab and a 2x12 cab in stock. so i think im on the way to building amps and selling and supporting them!

09/25/2021

its been a while since the last post. im part time now but still repairing tube amps and doing guitar setups plus electronic mods on guitars. the amp project now is getting two amps up and duplicatable. the issues have been making a reliable method of construction so the process is re creatable. i feel im there now. im building a 50 to 60 watt and the 35watt ive been working on for 3 years now.

04/28/2021

well, my leg is better. no more slipping off ladders for me. now that i know HOW to built my amp with everything in the right place i started on the 50 watter. the 35 watter is half way pulled a part to try out some new filter cans half the size of the old style types and they work very well and saves a lot of space! the 50 will have channel switching, power scale, sag, powered loop, 4,8,16 ohm taps for speakers. hope to have it done in the next couple weeks so i can take it to a jam at Ralston's Goat or some place in modesto! its been a long time coming. like going into 4 years!

03/16/2021

last nite i finished tweaking the overdrive channel tone controls and finishing up the artwork for the preamp, phase inverter and power tubes board. the improvements on the phase inverter raised the power out from 23 watts RMS to 35 watts RMS! Makes a big differences at these low output levels. the power amp has good projection from a 2x12" open back cab or a single 12" sealed back one of my studio customers generously donated to me. i really like these Greyhound speakers because this sound like Celesgions when overdriven and like Jensens when played clean in fender amps. the foot pedal is a single button small foot switch when plugged in overrides the front panel channel switch no matter what the front panel switch is set to. the Tube driven EFFECT LOOP works well. the weight of the amp is on the lite side even in the single 12" combo cab to be easily transported in a car and carried by hand for guys like me with a bad back. perfect club size amp for Rock, Blues, Country or Jazz or Top 40. put the amp on a chair or an am stand to get it off the ground and u will always here it even in a loud band and throw a mic in front of it

01/11/2021

Well, i turned 69 years old the day after Christmas. been working on amps and guitars nearly my whole life but its time to slow down. I' ll be concentrating my efforts on getting the shop cleaned up, city mill tax is due also. my first model tube amp is done and will be for sale later this year in limited numbers. Wish me luck!