I dug out my old Electro Voice EV 1144, and found out that one channel is not working. Right channel is fine, left is weak and scratchy. I traced back from the speaker terminals, and the speaker switch is OK, output fuses ok. Traced the signal to the output on the amp board and the right is fine, left is weak there. Power supply seems to be OK.
I am a decent electrician, but not an experienced repair guy. Not sure the next steps.
I do have a repair manual .pdf and that is mostly a schematic diagram and how to take the cabinet apart.
Any suggestions would be appreciated.
Here is the link to the service manual .pdf schematic is at the end of the document. http://archives.telex.com/archives/EV/Amplifiers/Service Manual/EV 1144A Service Data.pdf
I am a decent electrician, but not an experienced repair guy. Not sure the next steps.
I do have a repair manual .pdf and that is mostly a schematic diagram and how to take the cabinet apart.
Any suggestions would be appreciated.
Here is the link to the service manual .pdf schematic is at the end of the document. http://archives.telex.com/archives/EV/Amplifiers/Service Manual/EV 1144A Service Data.pdf
Is it for sentimental reasons? As far as performance goes it's really uninspired. Enough raining on your parade.
Since you have one good channel you can compare the voltages between the channels. They should natch pretty closely - <10%. Electronics tend to fail where things run warm or hot. This is usually final power transistors, drivers and power supplies. On a unit that old plan on removing the power transistors, cleaning off the old dried out heatsink compound and re-greasing the transistors with white heatsink compound.
Do you have a scope? Multimeter? Is there any DC on the speaker outputs? The speakers are scratchy but are the headphones? If the headphones are clean look for open emitter resistors, those 0.47 ohm units connected to the emitters of the power transistors. The power transistors _could_ go open but shorts are much more common. Are all the transformer windings good? They would read fairly low ohms with your meter. An open winding would require a new or rewound transformer.
G²
Since you have one good channel you can compare the voltages between the channels. They should natch pretty closely - <10%. Electronics tend to fail where things run warm or hot. This is usually final power transistors, drivers and power supplies. On a unit that old plan on removing the power transistors, cleaning off the old dried out heatsink compound and re-greasing the transistors with white heatsink compound.
Do you have a scope? Multimeter? Is there any DC on the speaker outputs? The speakers are scratchy but are the headphones? If the headphones are clean look for open emitter resistors, those 0.47 ohm units connected to the emitters of the power transistors. The power transistors _could_ go open but shorts are much more common. Are all the transformer windings good? They would read fairly low ohms with your meter. An open winding would require a new or rewound transformer.
G²
Status. Thanks for the answer. Yes it is for sentimental reasons. I bought new in 1967 and have had it since.
I have lots of other stuff around here like a couple of GAS Son of Ampzillas and NAD ETC.
I will try the headphones, but it is just a resistor in the final output circuit and the problem is upstream from that.
I do have a scope and a meter. I will follow your suggestion of measuring voltage in the amp. And will also check the transformers.
Thanks for your tips. I will try them tomorrow.
I am in LA as well
I have lots of other stuff around here like a couple of GAS Son of Ampzillas and NAD ETC.
I will try the headphones, but it is just a resistor in the final output circuit and the problem is upstream from that.
I do have a scope and a meter. I will follow your suggestion of measuring voltage in the amp. And will also check the transformers.
Thanks for your tips. I will try them tomorrow.
I am in LA as well
Thanks. I will check the electrolytics. I have used it on and off over the last 20 years. It probably has been 8 years since I tried to set it up in a system.
It does have a lot of sentimental value as it was my main system in my 20s.......lots of great music run through that amp.
I am planning on using it in small bookshelf system in my library......near my reading chair.
I know it is not exotic, but the design in interesting and it was one of the first solid state amps.....and I like the small package
It does have a lot of sentimental value as it was my main system in my 20s.......lots of great music run through that amp.
I am planning on using it in small bookshelf system in my library......near my reading chair.
I know it is not exotic, but the design in interesting and it was one of the first solid state amps.....and I like the small package
Hello,
I respect your harsh opinions on these ancient little amps, and I agree that they distort quite a bit, but on the other hand I must say that in my opinion they sound beautifully, particularly with rock, jazz and blues.
It could be for the very low feedback, or simply the effects of 2nd harmonics...
So before you throw away these little "wrecks", let me know !
I respect your harsh opinions on these ancient little amps, and I agree that they distort quite a bit, but on the other hand I must say that in my opinion they sound beautifully, particularly with rock, jazz and blues.
It could be for the very low feedback, or simply the effects of 2nd harmonics...
So before you throw away these little "wrecks", let me know !
I am NOT throwing it away.......lots of Stones, Janis, Cocker, Butterfield.... etc played on this thing. Lots of beautiful young things wooed with this EN 1144 in my apartments over my young years including my wife of 42 years!!
If this amp could only tell stories! We have been to Illinois, Indiana, New York, Quebec, California together.
It is part of the family.......I just have to fix it so I can use it again!! This is not a project, but a mission!!
If this amp could only tell stories! We have been to Illinois, Indiana, New York, Quebec, California together.
It is part of the family.......I just have to fix it so I can use it again!! This is not a project, but a mission!!
There are several on the market, don't know about that one. I think they all save time in troubleshooting, especially with the point-point type construction where it's a PITA to swap out parts. When I see electrolytics in the signal path that's the first thing I check, and they are usually in all OLD stuff. If you work on enough equipment to make it worth it go for it.
Craig
Craig
Lots of folks poo-poo the Mat Electronics $50 MUL-3333 but it actually works nearly as well as the Capacitor Wizard which is almost 5 times the price. The cheapy doesn't have a 'beep' but it reads the answers correctly. I have one at home and two at work. A lot of old gear has been improved with those meters.
SOME kind of ESR meter is a must have.
G²
This is the one I bought. Ana Tek Corporation
Already shipped FedEx....I should have in a couple of days.
Will keep you posted.
Already shipped FedEx....I should have in a couple of days.
Will keep you posted.
In or out of circuit, the voltage it outputs is NOT enough to turn on semiconductors, that's what makes them such a great tool. You can go through an entire piece of equipment in a few minutes and test for AC open capacitors. ESR meters are essentially AC Ohm meters, mine runs at 100KHz. The only thing you'll need to watch out for is capacitors that are DC shorted, a regular DMM will check for that. ESR are meters are great for testing those PITA twist-lock capacitors in lots of old equipment. If you do a lot of repairs you'll wonder how you got along without it.
Craig
Craig
It depends. The Cap Wizard and MAT boxes work by placing a low level (50-150mV 50-100KHz) signal across the cap and measure how much is shunted away. If the cap has a parallel 0.1uF ceramic it will read the ceramic even if the 'lytic is bad. In that case you need to lift one end of the 'lytic to measure it alone. Also remember that heating the cap will improve its performance. You'll see it deteriorate as it cools down.
SO; You CAN test in circuit but the unit must be powered DOWN. If it reads bad, it is. If it reads good it might not be. ESR depends on the value of the cap so it would be a good idea to get a few new caps of various values and test them to get a feel of how the meter responds. Also keep in mind some circuits REQUIRE a virtually perfect capacitor while others aren't so fussy. Switch mode power supplies require really good capacitors and the replacements MUST be very good quality. Panasonic FMs and Nichicon HM,HN and HZ series are good.
G²
You are correct about those SMPSs, that's why I got a Creative Electronics ESR meter, no longer made, close to 20 years ago. It help cut down the troubleshooting and repair time in those old 10' dish satellite receiver power supplies. Those SMPS would chew through capacitors fairly regularly. I still use that at work and I have a Capacitor Wizard at home. When I got these units there wasn't quite the selection there is now, there are many to choose from now. Once you get used to your particular ESR meter you'll learn it's characteristics and be able to troubleshoot very quickly. I wouldn't be caught without one now.
Craig
Craig
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