Recommended cap list for a 4010s Teac?

[tom3]

My Teac 4010s is working fine but I spot checked a couple of the PIO Suzuki caps and see they are reading at less than half the listed uF values. And those seem to be prone to total failure. I bought this machine back in 1969 and haven't touched any electronics. For sure I need to replace those caps and probably the motor run caps too. Is there a list anywhere of the usual cap replacements on this machine? SN 101090 with the AR40S preamp unit. And are those Suzuki caps polar? I don't see the usual neg. marking on these. Pretty amazing that this old machine still performs like it does (knock on wood). Thanks!

 

[rojoknox]

Greetings from RojoLand!

The Suzuki 0.1 µF 400 V "oil capacitors" must go — yesterday! They tend to fail short, and when they fail, they go Pop-BANG! and spew their guts (often taking other components out with them). Most of these are on the mechanical chassis, used as snubbers across switches, relays and solenoids. They are not polar, but should be replaced with snubber devices (0.1 µF cap in series with 120 ohm resistor, for example) instead of just a capacitor. I used to recommend a 0.1 µF 630 V poly film cap, but the snubber device is made for the purpose and is a better choice. I have a list I made up for my older A-4010S (S/N 48104; uses the RA-40S record amplifier) but it wouldn't be suitable for your later unit as it has a different schematic. You'll need the schemo found in the A-4010S *owner's* manual on HiFi Engine (that's right, the owner's manual!). It's the only place I've found the AR-40S schemo (on page 21), along with the later A-4010S mech schemo (page 20) which has the delay relay not found in my older rig. Use that schemo as a guide, but note where your rig may have a different component than that shown in the schemo; replace with what's there in the set if it differs. Note too that the mech schemo points out where a snubber device is specified rather than a plain cap. For instance, note the difference in symbol between C41, the snubber device across the brake solenoid, and C42, the capacitor (likely a Suzuki-bomb) across the capstan [pinch roller] solenoid. Use a snubber device for both. Some of these sets used green "lozenge-style" film caps instead of Suzuki-bombs; they should be OKeh but a snubber device is better.

Also, be advised that the motor control circuitry is connected directly to the AC line (it runs from the 100V tap of the transformer primary). DO NOT measure voltages against chassis ground! The ground point for such measurements is the negative side of C4 (100 µF 150 V). Chassis ground is appropriate for the audio circuitry.

Take care,
—
J. E. Knox "The Victor Freak"
Current caretaker of Teac A-4010S S/N 48104 (and twelve other R-2-R machines)

 

[tom3]

Thanks for the info. I dug into the transport today and made up a list for that. Kind of surprised to see those big can caps for the motors. I wonder if the multiple ratings are for the 50/60 cycle build on this. Going to be a little chore gettng to those caps behind the directional controls seems like. Is the 120 ohm series resistor deal to be used on all the the snubber caps? What wattage would those have to be? Getting up a list for Mouser. Some of those film caps are a bit expensive. My owner's manual does have that schematic, not a lot of parts info though. I also have an older service manual, seems like everything is different on mine. Going to be a winter project I'm thinking.

 

[rojoknox]

Greetings from RojoLand!

Yes, the smaller-value sections of the motor-run capacitors are for 50-Hz (and you needn't worry about them if you're in the USA or other 60-Hz area).

You'll need to unscrew and pull out the control assembly to get at the caps behind it; be careful putting it back together as it has to align with the faceplate, or the buttons will bind on it. You also need to beware pinching the wiring harness.

Snubber caps contain an internal 120-ohm resistor so you needn't worry about wattage. (There are parts with different R and C values as well.) This one at newark.com should do the trick: https://www.newark.com/roxburgh-emc/xe1201/arc-suppression-snubber-network/dp/01M9475

I looked on mouser.com for a similar part but found differing resistor values (none with 120 ohm, but that's not critical), superseded parts (Kemet) and expensive units from other makers (over $10 each—yikes!). That one on Newark is $3-and-change, cheaper in quantity, and is 0.1 µF/120 ohm, 250 VAC.

Take care,
—
J. E. Knox "The Victor Freak"

 

[tom3]

Like that signature "Retirement Home for Obsolete Technology", sounds like my basement.

 

[Chilibrother]

Timing is everything. Almost done restoring a 4010SL (sounds great btw) and I have a sack full of 0.1 µF 630 V poly film caps showing up tomorrow. So does something bad happen if I don't use an actual snubber @rojoknox ? It was so simple I knew it had to be a trap!

 

[tom3]

I could be wrong, probably, but I'm thinking the added resistor in the snubber circuit is more for solid state switching (transistor) that the old mechanical relays and switches.

 

[ARC Tech-109]

I just cut them out of my 4010S and went about my business, works just fine without them.
If you're going to recap the RA-40S I strongly recommend Nichicon or Panasonic caps and document everything as there are no legions or polarity markers on the board and I'd recommend replacing the PNP transistors in the playback amp. My noise floor dropped after replacing them and after that I took the shotgun approach and replaced all of them.

 

[Chilibrother]

I appreciate everyone's inputs - they seem to cover the entire spectrum. I'm going to take the middle ground and install the poly film caps I have sitting in front of me. My AR-40SL recording amp sounds dead quiet to me so I'm going to leave it be for the time being.

At the risk of being criticized for being lazy (I am) the four snubbers on the switch assembly seem the most problematical to change out. I see how it can be done by unbolting it and pulling it out forward but I will leave them alone for the time being. The way everyone describes the catastrophic failure mode is that they overheat and the internal pressure causes them to burst. I can see how that could happen on the snubbers for the solenoids and motors since they are energized the whole time the transport is engaged. But it seems like the switch snubbers would only carry current during the fraction of a second that it takes to press the buttons. Hard for me to imagine that causing explosive overheating but I could be wrong. If nothing else I will have a 75% reduction in the chance for disaster.

 

[ARC Tech-109]

Actually the caps are energized when the switches are open and snub the inductive kickback the instant the contacts open when depressed. Across the solenoids they are energized and absorb the flyback energy when de-energized to keep from arcing the switch contacts. The pinch roller solenoid can easily release 500V at that instant the current is removed.

 

[Chilibrother]

Thanks @ARC Tech-109 Like I said earlier it seemed too easy Not that bad, seems to be enough slack in the harness to pull the switch unit forward. Replacing caps on the "six-pack" for the motors has gone easier than I expected.

 

[rojoknox]

Timing is everything. Almost done restoring a 4010SL (sounds great btw) and I have a sack full of 0.1 µF 630 V poly film caps showing up tomorrow. So does something bad happen if I don't use an actual snubber @rojoknox ? It was so simple I knew it had to be a trap!

It'll probably be fine — since the original was just a cap. But since you have the SL model, note on the schematic where an actual snubber was used instead of a Suzuki-bomb. Snubbers are indicated with —< >—, caps with —| |—. Don't replace a snubber with a regular cap.

And hey — if you end up with leftover 0.1 µF 630 V poly caps, you could always build a tube amp…

Take care,
—
J. E. Knox "The Victor Freak"

 

[Chilibrother]

It'll probably be fine — since the original was just a cap. But since you have the SL model, note on the schematic where an actual snubber was used instead of a Suzuki-bomb. Snubbers are indicated with —< >—, caps with —| |—. Don't replace a snubber with a regular cap.

And hey — if you end up with leftover 0.1 µF 630 V poly caps, you could always build a tube amp…

Take care,
—
J. E. Knox "The Victor Freak"

Thanks for the advice. Not going to build a tube amp, but I have an H.H. Scott LK-30 that I just picked up and I know that it will take a pile of those!