Yamaha A-1 refurb recap re-relay and repost (binding)

brutal

YamaHoarder
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Out with the old.

There's a few of those pesky VD1212's in there that got replaced with series 1N4148* along with any fusistors and all the trimpots were replaced with Bourns multiturn units.
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FG series on the VR/MC amp board. All boards cleaned and defluxed after the rework.
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Mostly KW on the power board, yea overkill, but cheap enough for me when ordered in bulk from Mouser.
I may just start using KT (105* audio caps) for power if I can find all the right values.
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Raised the power trans heatsinks off board with a couple shoulder washers. There's a .47uf polar lytic still hiding in there still to be dealt with. I didn't clean the dust off well enough when I was gathering info to see it was not simply the same as the other one nearby.
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The A-1 already has polypropylene film bypass caps installed with the filter caps. Panasonic T-HA series and a couple ES Muse bipolars here. Preemptively replaced the speaker relay as I usually have a few of these popular relays in the bin.
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Vampire BPHEX goodness.
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Stock screw insert block removed intact and replaced with a solid delrin backing plate to mount the new posts.
A near perfect fit. No trimming required.
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Heatsinks get washed and new mica/thermal paste used just like Yamaha intended.
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Those OE Sankens are heavy duty puppies.
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No lytics whatsoever on the amp board.
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I felt a bit let down by all the A-1 hype when I first got it. I thought it was a little thin at first listen. It sounds fuller now than it did prior to the recap. Bass has more punch to it and the soundstage is slightly improved. I didn't get a chance to listen to any vinyl on it before, and don't own an MC cart, but surely the move from regular ol caps to FG series Nichicons should improve things. If nothing else, I know it's good for another 30 years.

Now if I could just get the idle current to adjust... :scratch2:
The SM wants a 8* 70W load connected to the speaker outputs during adjustment and I don't have anything built yet. Seems bench speakers aren't cutting it.

* I wasn't paying attention to the board markings and mis-oriented one of the 4148 series pairs used to replace the VD1212 regulator diodes. That little mistake caused a fair bit more work, one 2SA914 transistor and a grip of resistors.

Edit 12-18-2011 -- I seem to get a lot of PM's asking for parts lists.

As can be found readily on AK, VD1212 diodes are replaced with two 1N4148 or similar switching diodes wired in series.

Here's my Bourns Trimmer parts list, those used in the A-1 bolded:

Mfr PN MFR VALUE Watts Temp Range Dim Product
3299P-1-101LF Bourns 100 Horiz - side Trimmer, multiturn (pair on Amp Drive card)
3299P-1-201LF Bourns 200 Horiz - side Trimmer, multiturn
3299P-1-102LF Bourns 1k Horiz - side Trimmer, multiturn
3299P-1-202LF Bourns 2k Horiz - side Trimmer, multiturn (single 2.2K on PS card)
3299P-1-502LF Bourns 5k Horiz - side Trimmer, multiturn
3299Y-1-101LF Bourns 100 Vertical Trimmer, multiturn (pair on Pre-amp board)
3299Y-1-201LF Bourns 200 Vertical Trimmer, multiturn (pair 220 on Tone board) (pair 220 Ohm [VR301/VR302] on the VR/SW board for MC head amp distortion)*
3299Y-1-102LF Bourns 1K Vertical Trimmer, multiturn (pair on Electrolytic board)
3299Y-1-202LF Bourns 2k Vertical Trimmer, multiturn
3299Y-1-502LF Bourns 5k Vertical Trimmer, multiturn

This series of trimmer cases fit well on nearly every Yamaha I've redone. However, they do require the leads be bent to fit the PCB. I'll try to get a pic posted of the method I use.

Fusistors were replaced with metal film flameproof. Depending on voltage and current flow, 1/4W or 1/2W are preferred. However, all I had on hand were 1W so I'm risking some damage if there's a catastrophic failure. On the other hand, it's well known that transistors will always sacrifice themselves to protect their fusistors. :D My main goal was to provide stability and prevent drift that's common with the little buggers.

I used a common Omron MY02-DC12 for the speaker relay (5A)
Avionic has found a higher rated Panasonic(10A?) lately but I can't find his post.

*VR301 and VR302 (220 Ohm) are adjusted through a hole in this upside down board. If you replace them with 200 Ohm vertical pots, you will have to mount them on the back side (trace side) of the board and perform an adjustment that requires a distortion meter.
 
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Very nice pics. I recently repaired a couple of amps, and the sound improves as the caps take shape with use. I'm sure you know this~
 
Idle current on most Yammies is controlled by a three transistor circuit where one is mounted against the main heatsink, if one of them is bad adjusting the pot will have no effect. I had one of thos A-1s from the days when they first came out after twenty two years one of the dial lamps quit so I replaced them all.
 
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Wow. Fantastic work! The attention to detail is wonderful to see. Who machined the Delrin for you?
 
i'm recapping mine in the very near future. i'm just starting with the power supply though since i can reach those without taking anything apart. lamps need to be changed, too, but that looks like it also requires a bit more disassembly. it's good to hear it uses a common relay, unlike with the M-2/PC-2002. did you ever find a SM btw?
 
Idle current on most Yammies is controlled by a three transistor circuit where one is mounted against the main heatsink, if one of them is bad adjusting the pot will have no effect. I had one of thos A-1s from the days when they first came out after twenty two years one of the dial lamps quit so I replaced them all.

Thanks Rob. I was going to dive into the schematic and knowing that helps me along the path.
 
Wow. Fantastic work! The attention to detail is wonderful to see. Who machined the Delrin for you?

So far I've been lucky enough that simply cutting a right sized block on the table saw and some handy drill work has sufficed. The blocks you see are the pieces that come with the BPHEX. The Delrin I cut is just flat stock that provides the backing.

I've a similar project going on with a couple A-1000 with lesser quality, but still nice, Pomono red/black posts. That's a big 4"x6" Delrin plate.
 
Nice work! :tresbon:

How does it sound compared to the best of the other Yamaha stuff?

Good and getting better. Tonight I tracked down 4 of the 8 transistors responsible for stable idle current as wonky. They all pass a simple diode check, but fall down hard on hFE test. Guess they're just plum worn to a nub. I thought they seemed to be running way too cool, and I couldn't adjust idle current on either channel. Merrylander helped get me pointed north.

I also isolated the (preexisting) weak channel problem on my T2 I just finished recapping. A weak N-Channel JFET 2SK68A on the DC Post Amp board :banana:

I'll be putting another parts order in tomorrow.
 
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received my caps in very short order. those filter caps are a bitch to unsolder, though - i've never seen terminals quite like that. the long flat shape is making it difficult to get enough solder off to break the connection to the pad. now i'm completely out of wick and they're both still in there!
 
received my caps in very short order. those filter caps are a bitch to unsolder, though - i've never seen terminals quite like that. the long flat shape is making it difficult to get enough solder off to break the connection to the pad. now i'm completely out of wick and they're both still in there!

:yes:

Also know that there's no drain on them, so make sure you discharge them well (I drain with a resistor and measure until there's less than 500mv)

Were the terminal ends bent over? Mine were just poking straight up, but the size of the hole in the pad is uber tight with the cap terminal. Starting with a soldapult, then going to the wick as needed is the key to extending your wick supply :D - at least for those of use without an expensive rework station.

You may also have to work it on it's side, wiggle the cap a little as you heat/wick off the remaining solder. They need to be really dry and completely free of solder to get them out. Apply a little flux paste if you have some.

They're also glued to the board enough that you have to work something (90* dental pick) under the cap edge as much of the circumference that you can get to.
 
They're also glued to the board enough that you have to work something (90* dental pick) under the cap edge as much of the circumference that you can get to.

your advice is all good, and this last part is key. as i mentioned, ai'm trying to replace these caps and a few others without pulling any boards, and i don't think i'd have seen the glue otherwise. i know that one of the leads is basically free, but it wasn't pushing out at all and the glue helps to explain that.

and you were right (imagine that!) about how easy it was to pull those bulbs. i checked a local radio supply shop and they even have a good replacement in stock :yes: it will be nice to know when the A-1 is on without having to feel for heat.
 
received my caps in very short order. those filter caps are a bitch to unsolder, though - i've never seen terminals quite like that. the long flat shape is making it difficult to get enough solder off to break the connection to the pad. now i'm completely out of wick and they're both still in there!

I used a vacuum pump and a huge full sized soldering iron to do the ones on my CA-2010.
 
If you've got some old stranded copper wire and solder flux, you can make 'emergency wick".
 
If you've got some old stranded copper wire and solder flux, you can make 'emergency wick".

haha, that's a great idea. i really don't feel like running to the Shack tonight. i've got tons of crappy old speaker cable around here that should work well.
 
haha, that's a great idea. i really don't feel like running to the Shack tonight. i've got tons of crappy old speaker cable around here that should work well.

I've had too many inconsistent results with wick from Phones-n-crappy-Batteries-R-us, er Radio Shack to buy any more from them. I was ordering 10' mini reels from Mouser on occasion to keep the supply flowing, but now that MFR source has dried up so I'm ordering a 50' reel from a new supplier there this time around. Better be good stuff.
 
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