I picked this amp up cheap at a tag sale (really cheap) not to long ago. It has problems as the thing is about 40 years old. Both channels have a mains hum, and channel two is pretty flaky. Sometimes it will work, sometimes it won't. Now, because the amp is so old, i think i have only a couple of options.
1) Rebuild the amp, replacing cracked wiring and all the electrolytics, and other components. Remounting the output transistors with new insulators and thermal compound etc... This amp is very complex and difficult to work on, so i don't know if it would be worth the time/effort.
2) Tear everything out except the transformer and build a new amp into the chassis. This would be the most expensive of course, but possibly the better option. As far as i can tell, the power supply has +/-43vdc rails and an aux +/-18vdc. By looking at the schematic it seems to me both of these rails were filtered through the main caps, making it +/-61vdc. I'm not sure of this however so any help there would be appreciated. This is a 200/400w amp at 8/4 ohms so, i would have thought the voltage should be higher. The transformer is huge, around 1000va.
I have included a link to a zip file listing of the Altec amps. Please scroll down and take a look at the 9440 file.
Thank you for any assistance.
Altec Amplifiers
1) Rebuild the amp, replacing cracked wiring and all the electrolytics, and other components. Remounting the output transistors with new insulators and thermal compound etc... This amp is very complex and difficult to work on, so i don't know if it would be worth the time/effort.
2) Tear everything out except the transformer and build a new amp into the chassis. This would be the most expensive of course, but possibly the better option. As far as i can tell, the power supply has +/-43vdc rails and an aux +/-18vdc. By looking at the schematic it seems to me both of these rails were filtered through the main caps, making it +/-61vdc. I'm not sure of this however so any help there would be appreciated. This is a 200/400w amp at 8/4 ohms so, i would have thought the voltage should be higher. The transformer is huge, around 1000va.
I have included a link to a zip file listing of the Altec amps. Please scroll down and take a look at the 9440 file.
Thank you for any assistance.
Altec Amplifiers
Looks like its 81v rails and 43v rails (high and low power modes, They both get filtered through the same caps but they don't combine its either or). I have never seen an Altec amp before or much less heard one. It looks like a beauty though and I love the older stuff so personally I'd rebuild/repair it. It definitely needs caps. If the channel is intermitent I can't see it being a major fix (solder joints/connects).
Do NOT junk this amplifier or attempt to build some type of inferior piece of junk in its chassis.
This is an extremely good sounding amplifier when it has been gone thru and is working correctly.
I have had about ten of them in the last 15 yrs and wish I had saved several of them.
Clean the input contral as well as the bridge,100%/40% switch as this is a common problrm with them.
In addition to the cleaning replace the filter caps as they are very old and a common problem for this amplifier.
This is an extremely good sounding amplifier when it has been gone thru and is working correctly.
I have had about ten of them in the last 15 yrs and wish I had saved several of them.
Clean the input contral as well as the bridge,100%/40% switch as this is a common problrm with them.
In addition to the cleaning replace the filter caps as they are very old and a common problem for this amplifier.
I have gone through and cleaned the controls with cleaner. I will order some 10kuf/100v caps as soon as i can. I don't suppose you have a source to get some of a similar size so i don't have to change the mounting brackets?
I will look again and see if i can find the prblem with the 2nd channel.
Thanks for your help guys.
I will look again and see if i can find the prblem with the 2nd channel.
Thanks for your help guys.
Love the 9440.
Do not plug the boad edge connectors in wrong! Being off one pin will cause flames to shoot out of the board behind the front panel, as well as the channel you're working on.
In addition to the main filter caps, replace the input coupling cap (C1) and tack a 0.1µF film type in parallel. Do the same with the cap in the feedback loop (C3).
Increase C10 and C11 to 22µF, use 160V rated caps if they fit.
Suck all the solder out of the two sets of pins on the edge of the amp driver boards. Re-solder with 4% silver solder (original pins are gold and the solder joints fracture).
Don't mess with anything on the heatsink (unless it's fried).
22.000 Mfd 100V 2 1/2" Dia X 4" Tall + 1/8" w/screws new stock made by Hitachi $15.00ea
http://www.apexjr.com/new.htm
Do not plug the boad edge connectors in wrong! Being off one pin will cause flames to shoot out of the board behind the front panel, as well as the channel you're working on.
In addition to the main filter caps, replace the input coupling cap (C1) and tack a 0.1µF film type in parallel. Do the same with the cap in the feedback loop (C3).
Increase C10 and C11 to 22µF, use 160V rated caps if they fit.
Suck all the solder out of the two sets of pins on the edge of the amp driver boards. Re-solder with 4% silver solder (original pins are gold and the solder joints fracture).
Don't mess with anything on the heatsink (unless it's fried).
22.000 Mfd 100V 2 1/2" Dia X 4" Tall + 1/8" w/screws new stock made by Hitachi $15.00ea
http://www.apexjr.com/new.htm
Thanks for the suggestions djk. I will do these upgrades.
I saw the hitachi's at apexjr, and those look like the best deal around. I'll order up a pair when funds permit.
Keep the suggestions coming guys!
I saw the hitachi's at apexjr, and those look like the best deal around. I'll order up a pair when funds permit.
Keep the suggestions coming guys!
I took the old, original power supply caps into my shop today to test them on the benchtop Sencore meter. They were definetly bad, and not working. So, that explains the hum on both channels.
On the driver boards i replaced the small electrolytics with new ones, and some of the disc caps with film types. I am about to do the same for the control board as well. I still need to order the 22uf/160v parts and the main filter caps.
On the driver boards i replaced the small electrolytics with new ones, and some of the disc caps with film types. I am about to do the same for the control board as well. I still need to order the 22uf/160v parts and the main filter caps.
Excellent AJ! I'm glad to see you took the advice and decided to breath new life into the beast. Keep us updated with your progress. 
Alright, i replaced the caps on the driver board with new parts, and went to 22uf 160v parts for C10/11. The regular axial Nichicons i used fit perfectly. I bypassed the input and feedback cap with 100nf polyester parts as suggested. Lastly i replaced the .47uf film caps on the board with new polyesters as well.
I also resoldered all the connection pins on the driver board, and a few on the output boards, but i haven't had a chance to order the new power supply caps.
I also resoldered all the connection pins on the driver board, and a few on the output boards, but i haven't had a chance to order the new power supply caps.
This shows how fast i get things done... I finally got new Hitachi 22kufd/100v caps into the Altec. I reset the bias on both channels for 75ma as the service manual instructs, and both channels held at 75ma once warmed up. DC offset is low at 2-3mv for one channel, 30mv on the other.
Now, i still have a small amount of hum on the output of both channels and one channel does not give any real output, just distorted sound. When no signal is on that channel it has some noise plus the hum. Whats weird to me is that both channels go dead quiet if you turn the volume controls down. Looking at the schematics their is no circuitry between the input jacks and the vol. pots. Just wiring which looks fine. I haven't tried the xlr inputs. Anyone have any ideas?
Now, i still have a small amount of hum on the output of both channels and one channel does not give any real output, just distorted sound. When no signal is on that channel it has some noise plus the hum. Whats weird to me is that both channels go dead quiet if you turn the volume controls down. Looking at the schematics their is no circuitry between the input jacks and the vol. pots. Just wiring which looks fine. I haven't tried the xlr inputs. Anyone have any ideas?
Well, i found the problems i had with distortion on this amps was a combination of improperly set bias (must not have let that channel warm up long enough) and some cold solder joints on the unbalanced 1/4" connectors.
I knew the amp was working good, but i took it into shop today just to make sure with the oscope. I got a clean, prefect sine wave on the output of both channels. I only had a 20w 8ohm resistor to test with so i couldn't go to far with it, but i didn't see any crossover distortion or noise on the output.
Now, the question is what to do with the fully functioning amp. I have all the amps i really need for my stereo system but i could use it as a sub amp. I'm hesitating to use it because its worth a good amount of money and i've read that the driver and output transistors are unobtainium nowadays. For instance, if i decide to use it as a sub amp and next month the drivers die. What do i do? Are there substitutes available?
Thanks for the help with this amp.
I knew the amp was working good, but i took it into shop today just to make sure with the oscope. I got a clean, prefect sine wave on the output of both channels. I only had a 20w 8ohm resistor to test with so i couldn't go to far with it, but i didn't see any crossover distortion or noise on the output.
Now, the question is what to do with the fully functioning amp. I have all the amps i really need for my stereo system but i could use it as a sub amp. I'm hesitating to use it because its worth a good amount of money and i've read that the driver and output transistors are unobtainium nowadays. For instance, if i decide to use it as a sub amp and next month the drivers die. What do i do? Are there substitutes available?
Thanks for the help with this amp.
Altec 9440A
Hi
How does these amps sound ? Have the Altec 511B horn with 902 GPA drivers.
Are they up to the best solid state amps today?
Hi
How does these amps sound ? Have the Altec 511B horn with 902 GPA drivers.
Are they up to the best solid state amps today?
How important to replace the C10/C11 with 22uF instead of the original 10uF.
Why go for a higher capacitance ?
Updating the caps on my 9440A !
Why go for a higher capacitance ?
Updating the caps on my 9440A !
The sound of this cap changes how the bass sounds, I like the 22µF sound better.
It's not a huge difference, but when you are replacing all the tired electrolytics it's an easy change to make while you have the amplifier apart.
Leach uses 22µF in this position.
Harmon Kardon used 10µF film caps in this position in the Citation 16.
Crest uses 22µF plus a 1.5µF film on their high-volt rails in their CA series, they frequently use 220µF plus 2.2µF film on their low-volt rails.
Using the bigger cap values pretty much requires a moderate-sized film bypass, but the physical positioning and grounding of same is critical, so I don't go above 47µF (for a mono supply stereo amplifier, or 22µF in dual-mono amplifiers). If you choose to do so, use an oscilloscope and try adding a small resistor in series with the film cap to stop oscillations. The 0.47µF films in the 9440 are decoupled from the output stage by 10Ω resistors.
It's not a huge difference, but when you are replacing all the tired electrolytics it's an easy change to make while you have the amplifier apart.
Leach uses 22µF in this position.
Harmon Kardon used 10µF film caps in this position in the Citation 16.
Crest uses 22µF plus a 1.5µF film on their high-volt rails in their CA series, they frequently use 220µF plus 2.2µF film on their low-volt rails.
Using the bigger cap values pretty much requires a moderate-sized film bypass, but the physical positioning and grounding of same is critical, so I don't go above 47µF (for a mono supply stereo amplifier, or 22µF in dual-mono amplifiers). If you choose to do so, use an oscilloscope and try adding a small resistor in series with the film cap to stop oscillations. The 0.47µF films in the 9440 are decoupled from the output stage by 10Ω resistors.
Altec 9440A transistor replacement due to age ?
Curious to know, how many years may the transistors (6 pcs 2N3584 and 16pcs 2N6259) last.
Can one expect problem after +35 years ?
Any recommendation to replace these due to age ? Will transistors detoriate with age ?
Are these still available ?
Curious to know, how many years may the transistors (6 pcs 2N3584 and 16pcs 2N6259) last.
Can one expect problem after +35 years ?
Any recommendation to replace these due to age ? Will transistors detoriate with age ?
Are these still available ?
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