I will have to dig around in the filing cabinets. I think I have the service manual for these. I have 3 of them. 2 I use on different benches and 1 spare. If you haven't seen it here is a link to the factory Sencore video on the PA81. Someone was kind enough to digitize the VHS tape. th-cam.com/video/Yho0_uS06k4/w-d-xo.htmlfeature=shared It's kind of a corny sales video but does a good job of describing every function of the unit. It is worth a watch. They also made a divide by 10 input module for these. It took the 250W per channel or 500W in parallel maximum rating to 2500W per channel or 5000W parallel. I have personally never seen one. Occasionally I work on stage amplifiers in the 1,000 to 2500 Watt range. After years of being frustrated not being able to find the divide by 10 input attenuator I just ended up building one myself. Granted you don't want to be in the room when the fan kicks on when it starts to get hot. Sounds like a fighter jet taking off. Just used a large blower motor I had laying around when I built it.
Hi Mike, Thanks for the comment! You have my email if you happen to find a copy of the manual. If the address doesn't work, just comment again and I'll send you an email. I'll also check out the video. It should be entertaining! Happy holidays!!
Novalux Stereophonic channel has the video on his content. That unit originally sold for $1995 , BUT, it had a Sencore "Made Right Lifetime Warranty" which, I bet they won't honor unless you are the original owner and have the receipt.
Is this mike from "mikes radio repair" channel? I was wondering what happened to your channel? you just disappeared! Are you ever going to start up again? I'm sure that i am not the only one that hopes so!
I have owned my Sencore PA81 for the last 25 years, this is a awesome piece of test equipment. The DC balance will trigger at 1 volt and up, making it invaluable when troubleshooting equipment and saving speakers, the meters are extremely accurate when in-depth testing is required. This is perfect for solid state work of all makes, well worth it if you can find one.
I think the main reason they used an external power supply was to keep stray 60hz magnetic interference from coupling into the test equipment. The best way to do that is to remotely mount the transformer. Keeps cost down as well as you have to add more $ if the power supply is internal to keep the supply quiet.
Cool test equipment! I think every of a certain age loves those analog meters. I made many a mix tape back in the day. It was an art and deep dive into the vinyl….or someone else’s. Proprietary power to prevent boneheads from plugging in a poor power supply…..or did something change in the interim.
In the past, whenever I saw an audio amplifier analyser/tester I thought "pah, who needs that!" as it always seemed trivial to me to string a few power resistors together to simulate a load This, however, is quite a piece - a masterpiece probably. I am envious...
Excellent, i allways wanted one! But now i have bought R&S UPL which i have connected with self made dummy load which also contains additional LC load to simulate real conditions during amplifiers stability tests
15:35 Why didn't Sencore use 2 PCB transformers with multiple isolated output taps powered by mains voltage via a normal IEC connector on the back? For low power devices like this, that was the perfect solution, instead of placing a oscillator inside a sensitive measuring device. Like you mentioned, made over complicated :-) Neverless, a nice device to have on the bench. Grtz
Maybe trying to avoid NRL testing (eg, UL, CSA, etc, for North America, TuV for Germany, etc) for mains connected, and maybe small run equipment? Sencore always seemed a little weird to me though: it's not like they were cheap. EDIT: oh, and none of that would have worked with a battery since that seemed to be a requirement. Like the 8xxx series Fluke nixie multimeters. Battery was an orderable option so generating the 200V for the Nixies had to be done with an oscillator & transformer.
What a nice piece of test equipment Tony! Didn't know it existed. Thanks for showing the mod to a mains powered circuit! It's very applicable for a lot of situations. One which seem to come up fairly often for me. Appreciate the in depth explanation. Happy New Year! Really appreciate your skills and presentation. - jrh
Nice to see this thing on your bench, I also have one of these! :) Bought it from an old HiFi shop that closed some years ago, they sold off all the stuff out of the workshop. I handle a lot of HiFi equipment and guitar amps on my bench, so it's so usefull for me! Especially for tube guitar amps with the dummy load, the 16Ω option is really handy. I use it quite a lot and it still works great! :)
Oh, I love this thing. Hope to see it in action frequently on your future repairs. I rarely scream at the screen, but you made me this time. Supplying regulated 12V to the input of a 12V lineer regulator? C'mon... 🙂 If I were you, I would get rid of that LM317, get rid of the output adjustment circuitry and use an LM2940-12 fixed 12V regulator in there. Low(er) dropout, less heat, very good regulation and very good ripple rejection. The only downside may be that they are rated for 1A max, but that seems to be more than enough there.
what I have done for things like this is add a 15V reg to spread the heat out a little. But then i have also done it your way by adding 1 or 2 extra diode and using the voltage drop.
Never knew that something like this existed! I always wanted someone to make a multimeter that was aimed more at audio equipment repair, there are some multimeters that can do a 3 wire measurement and gives you voltage, amperage and watts displayed on its screen, I saw on the John Audio Tech channel an EEVBlog Bryman multimeter being used to measure a solar panels output. ... Really Cool but it doesn't do other stuff that I would love it to have... It's not a cheap meter either, if it did do a lot more for audio work and it cost $500 to $600, I would definitely get it, it would replace a lot of other equipment on the bench in which space is always precious! This Sencore unit definitely is very useful.... I could only find new replacement batteries and schematic or manuals for it, someone was selling the test leads for it asking around $400..... Can't imagine what is the asking price for the unit itself! Starting to look like it's going to remain in my wishlist for some time to come yet LoL 🤣....
That’s awesome Tony. Nice to see all this test equipment. I salivate on much of it 😂 Well I’m trying to backtrack your videos. You had a pioneer playlist. Somewhere I remember some rebuild kit for potentiometers. I have a bad pot on a SX-850. I also need a balance pot for a Mac1900. Wish me luck.
Never mind, I found it. Has nothing to do with my control, which is next to impossible to rebuild. Pioneer did a number on this one which made them unobtainium. Still would like to know where to get wafer kits.
Hi! Do you know (or does one of your faithful viewers know) where I can find the schematics to a Quadraflex 979 stereo receiver system? I have a bad channel on one side. Thanks for all your help and for these great videos!
Great Video. I have a PA81 on my bench but haven't used it much yet. This cleared up many questions in my mind. I was fortunate to get the Sencore power source with mine but it is nice to know there is a workaround if it fails. Would you mind sharing the component values you used? I think it is very common for these units to be sold without the original. Best, Doc
The barrel plug on the bad battery pack would not happen to be the same size as the long jack for the main power input, by chance, would it? If so, you could sacrifice the battery plug to DIY a power cord.
I have some of the calibration documents and other docs for this PA81 that I got from sencore many years ago, if you want a copy let me know and I can email them to you
What an awesome piece of equipment. I guess Santa came early for you this year? 😉 The most important question though: do you still have room on the bench? 😅
It's a very cool unit, I'm just a bit worried about all the complexity. Does it support bridged amplifiers? That's pretty much the standard these days with all the Class D amps out there. Any idea what the THD is like when you use it for attenuation and load? I had a look at the specs but it was not specified, only the dynamic range, but that's not very useful.
Ray Gianelli uses a Panasonic VP7725 that even does distortion measurements th-cam.com/video/_sW89ueWzR4/w-d-xo.html, Maybe that tops the Sencore PA81. Wall warts are not elegant but, as @martyh9309 already wrote they save you from stray magnetic fields. And, IMHO even more important, they save you from grounding the instrument.
I've wanted one of these for a long time, but they are way too pricey for my meager budget. I have a friend who has one, and he never uses it. BUT... he won't sell it either.
Wow! What a machine! Very, very interesting! Thank you for this one! I have to say that it's completely obsolete these days though. A simple setup of a computer, audio interface, voltage divider a bunch of load resistors and the right software is capable of everything the Sencore can do, plus so much more (spectrum analysis, THD and IMD, impulse response, you name it). I have built myself a switchable break-out box that can do 4-8-16 Ohms, (200W at 4Ohms), which goes into a good audio interface (THD+N= -113dB) through a voltage divider and a voltmeter per channel to monitor things, then straight into the computer. The rest is done by REW and ARTA, yet the options are many. The cost - well under $1000, including the laptop. The possibilities - limitless.
These device is by no means obsolete. I use mine daily and no computer interface can replace a well designed piece of test equipment that you can touch. When you want to be able to quickly diagnose issues it’s hard to beat the PA81
@@NovaluxStereophonic With all due respect, I'll agree to disagree. Obviously you're not following me, because ANY modern digital tech is far superior to the analog gear of the yesteryear, that's just a fact, given you're educated and not some kind of a believer. I fully understand why you like it, but by today's standards the Sencore is not a precise measuring equipment by no means. Also, when you want to quickly diagnose issues, you use a DMM, a signal generator and a scope, which none of them the Sencore is.
@@ampdoc I have tried digital interfaces at my bench and they are cumbersome for my specific workflow. Each tech is going to have a different preference. The PA81 is a supplemental device at my bench. I frequently use all of the devices that you mentioned but the PA81 just speeds things up for me.
Easy there your talking some homebrew setup with potential dividers and an audio interface etc your rattling of a load of stuff you have built and piped it into a bunch of free software ! you seem very exited about all of this but all your parts could add up to a croc of shit nobody here would swap with you over the Sencore I bet. I have used ARTA and REW myself and they are great but just saying the Sencore is obsolete because you DIYed something is a bit unfair .@@ampdoc
I think everybody has used the software and made there own interfaces but you can't beat a well built well spec'd instrument with a good pedigree like this, I'm a bit jealous of Tony !@@NovaluxStereophonic
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I will have to dig around in the filing cabinets. I think I have the service manual for these. I have 3 of them. 2 I use on different benches and 1 spare. If you haven't seen it here is a link to the factory Sencore video on the PA81. Someone was kind enough to digitize the VHS tape. th-cam.com/video/Yho0_uS06k4/w-d-xo.htmlfeature=shared It's kind of a corny sales video but does a good job of describing every function of the unit. It is worth a watch. They also made a divide by 10 input module for these. It took the 250W per channel or 500W in parallel maximum rating to 2500W per channel or 5000W parallel. I have personally never seen one. Occasionally I work on stage amplifiers in the 1,000 to 2500 Watt range. After years of being frustrated not being able to find the divide by 10 input attenuator I just ended up building one myself. Granted you don't want to be in the room when the fan kicks on when it starts to get hot. Sounds like a fighter jet taking off. Just used a large blower motor I had laying around when I built it.
Hi Mike,
Thanks for the comment! You have my email if you happen to find a copy of the manual. If the address doesn't work, just comment again and I'll send you an email. I'll also check out the video. It should be entertaining! Happy holidays!!
Novalux Stereophonic channel has the video on his content. That unit originally sold for $1995 , BUT, it had a Sencore "Made Right Lifetime Warranty" which, I bet they won't honor unless you are the original owner and have the receipt.
Is this mike from "mikes radio repair" channel? I was wondering what happened to your channel? you just disappeared! Are you ever going to start up again? I'm sure that i am not the only one that hopes so!
I have owned my Sencore PA81 for the last 25 years, this is a awesome piece of test equipment. The DC balance will trigger at 1 volt and up, making it invaluable when troubleshooting equipment and saving speakers, the meters are extremely accurate when in-depth testing is required. This is perfect for solid state work of all makes, well worth it if you can find one.
Tony I’m jealous! I’m anxious to see how you incorporate this into your lessons. I’m happy you have this new test gear in your arsenal.
I think the main reason they used an external power supply was to keep stray 60hz magnetic interference from coupling into the test equipment. The best way to do that is to remotely mount the transformer. Keeps cost down as well as you have to add more $ if the power supply is internal to keep the supply quiet.
Cool piece of test equipment, looking forward to seeing how it's used in the future!
Cool test equipment! I think every of a certain age loves those analog meters. I made many a mix tape back in the day. It was an art and deep dive into the vinyl….or someone else’s. Proprietary power to prevent boneheads from plugging in a poor power supply…..or did something change in the interim.
Valuable insight into psu design as well as a fascinating review. Many thanks and seasons greetings !
In the past, whenever I saw an audio amplifier analyser/tester I thought "pah, who needs that!" as it always seemed trivial to me to string a few power resistors together to simulate a load This, however, is quite a piece - a masterpiece probably. I am envious...
Very nice, well designed test gear! And your mods to suit your test situation seem very good. Happy holidays to you and your family, Tony!
Nice score on the Sencore PA81. You don't see those around very often. Great piece of audio test equipment.
Excelente equipo Tony, la verdad que muy completo. Y muy bien lo que hiciste con la fuente, yo hubiese hecho lo mismo.
Excellent, i allways wanted one! But now i have bought R&S UPL which i have connected with self made dummy load which also contains additional LC load to simulate real conditions during amplifiers stability tests
15:35 Why didn't Sencore use 2 PCB transformers with multiple isolated output taps powered by mains voltage via a normal IEC connector on the back?
For low power devices like this, that was the perfect solution, instead of placing a oscillator inside a sensitive measuring device.
Like you mentioned, made over complicated :-) Neverless, a nice device to have on the bench. Grtz
Maybe trying to avoid NRL testing (eg, UL, CSA, etc, for North America, TuV for Germany, etc) for mains connected, and maybe small run equipment? Sencore always seemed a little weird to me though: it's not like they were cheap. EDIT: oh, and none of that would have worked with a battery since that seemed to be a requirement. Like the 8xxx series Fluke nixie multimeters. Battery was an orderable option so generating the 200V for the Nixies had to be done with an oscillator & transformer.
A possible reason for using an external power source is that only the power source would have to meet UL requirements.
What a nice piece of test equipment Tony! Didn't know it existed. Thanks for showing the mod to a mains powered circuit! It's very applicable for a lot of situations. One which seem to come up fairly often for me. Appreciate the in depth explanation. Happy New Year! Really appreciate your skills and presentation. - jrh
Nice to see this thing on your bench, I also have one of these! :) Bought it from an old HiFi shop that closed some years ago, they sold off all the stuff out of the workshop.
I handle a lot of HiFi equipment and guitar amps on my bench, so it's so usefull for me! Especially for tube guitar amps with the dummy load, the 16Ω option is really handy. I use it quite a lot and it still works great! :)
That power plug very much looks like a DIN 45323 , this plug is also used on the PM8907 power supply of the Fluke / Philips PM97 scopes.
Oh, I love this thing. Hope to see it in action frequently on your future repairs. I rarely scream at the screen, but you made me this time. Supplying regulated 12V to the input of a 12V lineer regulator? C'mon... 🙂 If I were you, I would get rid of that LM317, get rid of the output adjustment circuitry and use an LM2940-12 fixed 12V regulator in there. Low(er) dropout, less heat, very good regulation and very good ripple rejection. The only downside may be that they are rated for 1A max, but that seems to be more than enough there.
what I have done for things like this is add a 15V reg to spread the heat out a little.
But then i have also done it your way by adding 1 or 2 extra diode and using the voltage drop.
8:23 - "I recommend the under-coating as well..." :)
Never knew that something like this existed! I always wanted someone to make a multimeter that was aimed more at audio equipment repair, there are some multimeters that can do a 3 wire measurement and gives you voltage, amperage and watts displayed on its screen, I saw on the John Audio Tech channel an EEVBlog Bryman multimeter being used to measure a solar panels output. ... Really Cool but it doesn't do other stuff that I would love it to have... It's not a cheap meter either, if it did do a lot more for audio work and it cost $500 to $600, I would definitely get it, it would replace a lot of other equipment on the bench in which space is always precious!
This Sencore unit definitely is very useful.... I could only find new replacement batteries and schematic or manuals for it, someone was selling the test leads for it asking around $400..... Can't imagine what is the asking price for the unit itself! Starting to look like it's going to remain in my wishlist for some time to come yet LoL 🤣....
That’s awesome Tony. Nice to see all this test equipment. I salivate on much of it 😂
Well I’m trying to backtrack your videos. You had a pioneer playlist. Somewhere I remember some rebuild kit for potentiometers. I have a bad pot on a SX-850. I also need a balance pot for a Mac1900. Wish me luck.
Never mind, I found it. Has nothing to do with my control, which is next to impossible to rebuild. Pioneer did a number on this one which made them unobtainium. Still would like to know where to get wafer kits.
Good video as always. (I always want sushi after watching that bamboo stick...)
Just use an AC input jack with integrated Fuse and Powerswitch on the back if you want the independent ON/OFF switch.
What a cool test device..if you work on ANY type of power amp stage.
Thanks Tony. Merry Christmas, Mate.😊
Tony Sencore had tech tips they provided free on how to use their equipment. TT-163 covers this unit.
Thank you for sharing that!! I'll be sure to check it out.
Great piece of equipment.
5:23 Aren't these loudspeaker drivers a bit too close to the meters?
It's interesting that both are held by only 3 bolts.
Hi! Do you know (or does one of your faithful viewers know) where I can find the schematics to a Quadraflex 979 stereo receiver system? I have a bad channel on one side. Thanks for all your help and for these great videos!
Can you please give the link to download schematic diagram of this analyser at the perfect quality as in the video?
Thank you and best regards!
I want one of these!
57:10 - Does that measure *real* watts or does it just measure the voltage and calculate watts from the load selected?
Great Video. I have a PA81 on my bench but haven't used it much yet. This cleared up many questions in my mind. I was fortunate to get the Sencore power source with mine but it is nice to know there is a workaround if it fails. Would you mind sharing the component values you used? I think it is very common for these units to be sold without the original. Best, Doc
The barrel plug on the bad battery pack would not happen to be the same size as the long jack for the main power input, by chance, would it? If so, you could sacrifice the battery plug to DIY a power cord.
V regs require more headroom than just the dropout voltage... For the least ripple, a minimum of at least 3 volts is needed.
Does the power supply noise with the bench power supplies have an effect on measurement on this device ?
Looks Great👍
I would have put a power switch on the rear panel.
I have some of the calibration documents and other docs for this PA81 that I got from sencore many years ago, if you want a copy let me know and I can email them to you
What an awesome piece of equipment. I guess Santa came early for you this year? 😉
The most important question though: do you still have room on the bench? 😅
Yup he did
It's a very cool unit, I'm just a bit worried about all the complexity. Does it support bridged amplifiers? That's pretty much the standard these days with all the Class D amps out there. Any idea what the THD is like when you use it for attenuation and load? I had a look at the specs but it was not specified, only the dynamic range, but that's not very useful.
How are the scope outputs driven still keeping the speaker commons isolated? Transformer?
Ray Gianelli uses a Panasonic VP7725 that even does distortion measurements th-cam.com/video/_sW89ueWzR4/w-d-xo.html, Maybe that tops the Sencore PA81.
Wall warts are not elegant but, as @martyh9309 already wrote they save you from stray magnetic fields. And, IMHO even more important, they save you from grounding
the instrument.
Where on your bench are going to fit that ? 😂
Wow, that's quite a toy! I'm jealous haha
👍
I've wanted one of these for a long time, but they are way too pricey for my meager budget. I have a friend who has one, and he never uses it. BUT... he won't sell it either.
All of the ICs and processors but they still use analog meters lol Congrats
Wow! What a machine! Very, very interesting! Thank you for this one! I have to say that it's completely obsolete these days though. A simple setup of a computer, audio interface, voltage divider a bunch of load resistors and the right software is capable of everything the Sencore can do, plus so much more (spectrum analysis, THD and IMD, impulse response, you name it). I have built myself a switchable break-out box that can do 4-8-16 Ohms, (200W at 4Ohms), which goes into a good audio interface (THD+N= -113dB) through a voltage divider and a voltmeter per channel to monitor things, then straight into the computer. The rest is done by REW and ARTA, yet the options are many. The cost - well under $1000, including the laptop. The possibilities - limitless.
These device is by no means obsolete. I use mine daily and no computer interface can replace a well designed piece of test equipment that you can touch. When you want to be able to quickly diagnose issues it’s hard to beat the PA81
@@NovaluxStereophonic With all due respect, I'll agree to disagree. Obviously you're not following me, because ANY modern digital tech is far superior to the analog gear of the yesteryear, that's just a fact, given you're educated and not some kind of a believer. I fully understand why you like it, but by today's standards the Sencore is not a precise measuring equipment by no means. Also, when you want to quickly diagnose issues, you use a DMM, a signal generator and a scope, which none of them the Sencore is.
@@ampdoc I have tried digital interfaces at my bench and they are cumbersome for my specific workflow. Each tech is going to have a different preference. The PA81 is a supplemental device at my bench. I frequently use all of the devices that you mentioned but the PA81 just speeds things up for me.
Easy there your talking some homebrew setup with potential dividers and an audio interface etc your rattling of a load of stuff you have built and piped it into a bunch of free software ! you seem very exited about all of this but all your parts could add up to a croc of shit nobody here would swap with you over the Sencore I bet. I have used ARTA and REW myself and they are great but just saying the Sencore is obsolete because you DIYed something is a bit unfair .@@ampdoc
I think everybody has used the software and made there own interfaces but you can't beat a well built well spec'd instrument with a good pedigree like this, I'm a bit jealous of Tony !@@NovaluxStereophonic
Does it measure IM distortion, as well as harmonic?
No, it doesn't.
...you may be an 'idiot' but you're not a dummy
Nice toy! Thanks for the look and your skills!