Hi I'm new to the site so hi to all I have a audio innovations alto mk1 in black there are plenty of discussions to read about this amp but i cant find anything regarding strip down procedure as I'm going to recap it shortly, has anyone got a tutorial for me or if you have done this can you provide me with a description of how you went about it if at all possible, thanks
You will be helped by the descriptions of the operation of the JLH1969 and JLH1996 amplifiers (general topology correspondence).
The difference between Alto in the use of discrete Darlington transistors at the output and a lower quiescent current. Complies with class AB.
Power supply without features. There is a circuit with a delay relay for turning on the outputs.
#8 Audio Innovations Alto
General recommendations for cleaning and restoring old amplifiers. Many people note the poor quality of PCB 🙁
The difference between Alto in the use of discrete Darlington transistors at the output and a lower quiescent current. Complies with class AB.
Power supply without features. There is a circuit with a delay relay for turning on the outputs.
#8 Audio Innovations Alto
General recommendations for cleaning and restoring old amplifiers. Many people note the poor quality of PCB 🙁
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Thanks I’ll have a look but the easiest way would be take pics of each step and can the adjustments be done with just a volt meter or do I need an oscilloscope thanks
I don't use a scope. Most things can be done with a DVM but most are insensitive to AC frequencies over 7000 hz. The $30-40 DVM I've owned have produced random numbers on music, but work fine on 60 hz.
For checking for ultrasonic oscillation after repair or at startup I use an analog VOM on 20 vac or even 50 vac scale. They cost $20-30 and work fine for silent oscillation check, also checking power out of amp (speaker voltage). I saw an anlog VOM with 15 VAC scale for $25 at the Rural King store last week. Cheapest test of rail caps of an old amp is measure speaker voltage at just before clipping, then compare to power rating in sales brochure.
If you have problems with the input stage of an amp or a line level preamp or mixer, a $100 analog VOM with 2 vac scale may be necessary. But VAS & later a 20 vac or 50 vac scales are fine.
Advantage of no scope, no 100 electrolytic capacitors to go bad. My analog VOM is 34 years old, has no dried out caps to replace. Also when I step on the probe, it doesn't cost $50. I put 30 e-caps in a scope last year but it is too big to fit on my repair table so I'm still not using it.
If a silent voltage is detected, you can prove it is ultrasonic by changing the DC blocking cap series the negative probe (usually .047 uf 200 v) on the analog VOM to 390 pf. Music flows right through a .047 uf cap, but ultrasonic oscillations are blocked by tiny capacitors.
For checking for ultrasonic oscillation after repair or at startup I use an analog VOM on 20 vac or even 50 vac scale. They cost $20-30 and work fine for silent oscillation check, also checking power out of amp (speaker voltage). I saw an anlog VOM with 15 VAC scale for $25 at the Rural King store last week. Cheapest test of rail caps of an old amp is measure speaker voltage at just before clipping, then compare to power rating in sales brochure.
If you have problems with the input stage of an amp or a line level preamp or mixer, a $100 analog VOM with 2 vac scale may be necessary. But VAS & later a 20 vac or 50 vac scales are fine.
Advantage of no scope, no 100 electrolytic capacitors to go bad. My analog VOM is 34 years old, has no dried out caps to replace. Also when I step on the probe, it doesn't cost $50. I put 30 e-caps in a scope last year but it is too big to fit on my repair table so I'm still not using it.
If a silent voltage is detected, you can prove it is ultrasonic by changing the DC blocking cap series the negative probe (usually .047 uf 200 v) on the analog VOM to 390 pf. Music flows right through a .047 uf cap, but ultrasonic oscillations are blocked by tiny capacitors.
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There are two (four) pots in the amplifier. VR1,2 setting of the bias current. VR3.4 midpoint setting. Ten electrolytic capacitors. Unreliable PCB.
Little heatsinks.
Little heatsinks.
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The amp still works fine, I opened it to clean and noticed a badly bulged cap at the back 10000uf so before it does break down I decided to replace all of them as I’ve read they go out of phase with age, I’m just stuck at setting the bias I thought I might need a oscilloscope, I was asking as well is there a strip down procedure to follow just to make it more straight forward but I’ll figure it out, thanks
About installing bias is written in the manual # 2.
Use a 10000 uF electrolytic capacitor for a voltage of at least 63V and 105 C.
Use a 10000 uF electrolytic capacitor for a voltage of at least 63V and 105 C.
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I managed to get the original parts 10000uf 63wv 85c made by samwha, I read keep it as original as possible so you don’t change the sound, rapid electronics online about 25 quid for the caps and speaker protection relay
I have the chrome amp as well in perfect working other cam with after market remot but works all functions, as stated there is a real sound difference the mk2 sounds much flatter the mk1 is far more musical
I have the chrome amp as well in perfect working other cam with after market remot but works all functions, as stated there is a real sound difference the mk2 sounds much flatter the mk1 is far more musical
If you seek disassembly instructions on this particular amp you need to put "audio innovations alto mk1" in the thread title. Not every poster reads every post, particularly the pros. I don't recognize this as a high volume model, however.
I was going to call the thread what you suggest but there’s a few with that title I thought it might be more successful as I wanted help with disassemble of the amp, thanks I’ll look at changing the name of the thread