Fix For Poor Sounding Pioneer SPEC 2 Power Amplifiers. Vintage Stereo Repair & Restoration.
ฝัง
- เผยแพร่เมื่อ 27 พ.ค. 2023
- Can Be One Of The Best Sounding Amps With This Change.
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Mine sounds amazing though an M-77. Had it changed to 120 Volt when ordered from Japan. Paid a few hundred to upgrade and it's brilliant
$8 part, a little time, help from an old friend and this baby is spared from the landfill. Loved the warm up demonstration, really showed the importance of doing it. Thanks from Colorado.
Thanks Craig.
Bravo. What a fantastic video. The description of the DIY process and the commentary, in conjuction with realtime graphs of the mV vS. T, will help a lot of viewers comprehend the way in which this old equipment operates. Once again, thank you for your efforts.
Your welcome. Thank you for your kind words and for watching.
Hello, I follow your channel very carefully, they are a great help for those of us who are not technical, they are a great help, I am very pleased to share your great knowledge, detail and patience with us.
Sometime so easy to get an amp running at his best - thanks for sharing.
Another great lesson , Thanks Chris !!!
Thank you for watching.
Many thanks for your videos, I love watching them
Your welcome and thank you.
Thanks for the very informative video!
Thank you for watching.
Many thanks for the video.
Your welcome. Thank you for watching.
Hi Cris I have 2 spec 2s. I can’t work on my own equipment I have tremors in my hands but may take them to a tech my friend s don’t like their sound quality and I have to agree.if I could change out those 2 relays I may be more impressed I do love Pioneer from the 70s very well made !!
hi Chris great video i build all my own tube audio gear
Hey Ian, thanks. I've never built any tube gear from scratch. I bet it's fun. The closest thing was rebuilding a Dynaco 70 that was held together with duck tape.
Thanks well done
thank you chris
Thanks for watching.
Good job dude
Thanks!
Good overall, but I think it would help people's understanding if you touched on the relationship between bias voltage, which you're measuring, and bias current being adjusted. I'm guessing there might be a 1 or 0.1 ohm sense resistor, but I didn't hear a connection mentioned.
Bought a Spec 1 and Spec 2 for $20 each at a charity tent sale a few years ago. The amp had that crappy sound of low bias and after hitting all the wrap posts with a soldering iron it's been fine for near 10 years. Never did get the preamp working. It powers up but no signal on the output end. Time for another look now that I am retired.
I had a friend who had one years ago....When he turned it on, it TRIPPED his 200 amp Square D main breaker. Back then I was half afraid to look at something like that....I think he gave it away. I had heard that IF the soft start was not working, it would draw a major amount of current, trying to charge up those enormous filters. I'm also thinking that main breaker was a little flakey, as it didn't trip the branch circuit. I had a Dynaco stereo 400, that only had a speaker relay, and no soft start. Just wondered what you thought about that? PS...great video!...
Thanks for watching. If it tripped a 200 amp breaker and shut off the house I'd be afraid too, lol. All the companies had different design schemes. I have a Dynaco 400 also. It's much a simpler design then the SPEC-2 and not built as well but it still works after all these years.
Great video, very helpful info. Question: what is the function of that Reed relay? And what is the failure mode, high contact resistance, or failure to pull in ( coil issue)?
Thanks for watching. This relay is used in the SPEC-2 to interrupt the flow of current in the bias section during power up to prevent "Thumps" from your speakers. I really don't know the answer to the failure mode. They seem to fail differently in different SPEC-2's. Some cause the bias go low and stay there like this SPEC-2. Others the bias goes low and then back to normal. Others the bias goes to absolute zero. Certainly sounds like a contact issue but I don't know.
We carried pioneer. But opted out of the spec separates .for the price ,honestly there were better choices on the showroom. Dynaco 400, citation 16 and Marantz among others. It's believed by some that this was pioneers stab into the heavy hitter separates .but audibly fell short of the mark.
Great video thanks. Hey what did you use for the graphing for this video?
Thanks. I used my Siglent SDM3045X multimeter's USB output to my Windows 10 PC running the meters utility software called EasyDMM. I use Divinci resolve for video editing. That's how I got the SPEC-2, multi-meter display etc. into the graph. I then used Flashback express to capture the screen in real time and save it in .mp4 video format.
Very interesting. But what is exactly going on with this warming up? I mean it's not like capacitors are beging topped off or something...so I'm confused.
Frankly, I'm not an expert. Google is your friend and people who design this type of A/B class amplifier can better explain the time/heat/current bias ratio then I ever could. Thanks for watching.
Hi Chris! Love your videos! Where do you live? Do you work on CROWN components?
Thanks! I live in east central Florida. I'm not a professional so I only work on equipment in my collection but that does include some Crown gear.
Thanks for another great video I learned more every time I watch your videos spec 2 are cool never had one I went to an estate sale yesterday found two Kenwood KR 9600 they're pretty grubby I'm sure they need work I'll eventually get around to them but I couldn't pass them up the woman said they don't work her husband never got them going she said just give me $25 for both I thought I iim in Dreamland but she was serious everything there was incredibly cheap wow I thought I'd never find cheap stereos anymore but nope they had to go she's moving to Florida and everything has to go so that was fun thanks have a great holiday
Thanks for watching. Wow, great deal on the Kenwood's! Those are really nice receivers. Good luck on getting them going.
KR are laid out nicely inside and easy to work on. I recently did one and the input selector was comically oxidized. Well beyond a deoxit flush. I removed it and polished it shiny new with metal polish. Good luck.
reminds me of my trip to a charity tent sale a few years ago where I picked up a Spec 1 and Spec 2 for $20 each. They both looked great but needed work. The amp kicks ass after chasing down poor connections on those wrap posts. The preamp is still under the bench waiting for another rainy day when I get ambition.
👌👌👌
Chris, thanks for another great video..... just curious what is that other Reed relay for next to the one you replaced?
Your welcome. I think that's the one used for when you are switching between 4 and 8 ohms via the switch on the rear panel. I think that's right but I'm just recalling it off the top on my head.
@vintageaudioaddict That's sounds right....In my industry, these were used in many controllers and switches!
you would think you would see crossover distortion on the cro with low bias
For sure, what you wrote is true. The problem is that most folks who own vintage audio gear don't have the test equipment to see the distortion. They only have their ears. I wanted to show in this video that just because you have a left and a right channel playing it doesn't mean that it's operating correctly. Most vintage audio gear like this SPEC-2 can sound great if it's working properly but most vintage audio gear is not working properly in some manner.
Would a bad reed relay cause the Spec-2 to go into protection mode after a period of normal operation?
I haven't heard of any of them having that problem with this relay being the issue. Not saying it can't I just haven't seen it.
I have the Pioneer Spec. 1 & Spec 2 and hardly any volume from the Left channel. It used to get better after on for about 10 min., but no longer. What do you suspect the problem to be? All connections are fine.
you say all the connections are fine but I bought mine "not working" a few years ago and the problem was those connections at the wrap posts on the boards. Ran new solder and everything has been fine years later. BTW, paid $20 for it.... and it's in perfect cosmetic condition.
Does the Pioneer A-27 have this problem also ?
Really not sure. I have a A-27 but I don't remember these relays.
Get the schematics for both the SPEC 2 and the A-27, and compare them - see if the A-27 uses the soft-start circuit. If so, you should consider replacing those relays at some point.
I didn't get the last part, are you saying that nominally, even when the spec is working properly, it must warm up for 30 minutes before being listened to?
I believe he is saying that everything sounds ok, but not perfect (measured) till it settles down. Mine sound great in the time it takes to select some program material. I suspect aging caps may be an issue, but never dug into it. BTW, mine is all original except for some touched up solder joints on the wrap posts. IOW, base on mfgr date, these things are over 40 years old.
So I have to turn it on 30 minutes before I listen to music?
No, you can listen to it whenever you want too.
I was just kidding. I have an interest in repairing vintage audio gear and enjoy watching your videos. I love the challenge of troubleshooting. I have an old 1978 Kenwood KA5300 tuner that does not work. I had it open one day and was playing around. I sprayed contact cleaner on the tuner fins and it’s never worked since. I am saving it as a rainy day project for when I retire. Thank u for the knowledge and entertainment.
Whats the difference between taking it apart and "going ahead and taking it apart" why keep saying "go ahead" ???
Couldn't just clean up the relays strange