ST-120 Rectifier Choices

Bob,

I've had some problems with my ST-120 blowing up. Some time back you had me replace the cap-can, and that helped a lot. But a couple of weeks ago I did it again; I turned off the ST-120, then (mistakenly) turned it right back on. It blew the slo-blo fuse, it flashed the Ruby 5AR4 rectifier tube, and apparently took out a KT-88 (or two).

I replaced these three items (fuse, rectifier, and KT88) and all has been fine, but I'm still nervous.

I didn't know about the potential use of a Weber WZ68 on my ST-120. Would this help?

I have ordered a Weber Copper-Cap GZ34, plus I bought a GZ33/CV5745 Mullard NOS tube off eBay that you mentioned somewhere, plus I also have "1 NEW IN THE BOX 1961 MULLARD GZ34 5AR4 TUBE" that I just won on eBay coming in.

My ST-120 is on a big APC UPS, in order to avoid momentary power outages.

Can you take a moment to describe rectifier tube choices on the ST-120, and their pros and cons, especially with regard to holding up to power cycling.

Thanks!

PS: I've also 'upgraded' by power cord to a 3-wire grounded cord, and attached the ground to the chassis. Was this a good or bad move?

Duh. I now see the thread just a couple of posts lower "Choices in rectifier tubes for VTA?" that does have some of the discussion I was looking for. But I am still interested in the use of the WZ68 in the ST-120, so anything else that can be added to this discussion would be greatly appreciated.

Thanks!

Bob,

Thanks, as always. I'm ordering a Weber WZ68 or two right now.

Bob,

I would say you're spot-on that most of the rectifier problems I've had were caused by my short cycling, and I really try to not do it. The last time was an accident... muscle memory.

As I said, I do have a big APC UPS on the ST-120 to avoid externally-caused power interruptions. But that begs the question; In the 60's through the 90's, when UPS's were rare, did this condition cause many, many failures during storms or other events causing short-term power interruptions?

And, do amps like the McIntosh MC2102 do something in their circuit design to avoid this? Is there something more I can do?

A cool upgradge would be an add on board that waited like a minute before applying power to the amp (of course that would add to startup delay).

Like this one (but it's for 220V):

http://www.electronics-project-design.com/DelayTimer.html

They are used in Home A/C's to protect compressors from restart after power failure.

Jason

Bob,

That's a good point. I think a "non-latching" GFCI will do that. Most of the ones on our walls (if you have a new enough house, or have added them) are latching types, meaning they don't trip during a power interruption.

However, I do believe there are power strips out there that will do just this, though it's probably not easy to find one, as most people would get annoyed by it. Who's wants to root around behind the TV console after a power outage to reset the GFCI?

That's a good solution for the power interuuptions. Might be good to buy one to run tube amps from. Then just to remember NOT to turn it back on within a minute.

I'm going to look on the wonderous google and ebay and see what turns up.

Jason

Many separate power strips that have a GFCI (they are sold for use with power tools on outdoor construction sites) have a GFCI of the nonlatching type.

GP49,

do you have any one you know of?

I did a quick google and the Stanley and Tripplite for construction sites looked good (except for the bright yellow) but in their descriptions never mentioned non-latching, or tripped with power failure.

Jason

.

It looks like it's what I was looking for. Amazon has the plug in one, but without the strip, about $20 for the white, only $17 for yellow. Probably go with yellow.

I might buy two, one for my old radio.

Website says it cuts off and require manual reset. 25 ms reaction time.


Thanks.

Outside of using a really good power filter unit that are made primarily for digital home theatre systems that include outlets that stay off after a power interruption, I've heard of people using magnetic power switches to prevent short cycling once a power interruption has occurred.

See these website addresses:

http://www.rockfordsystems.com/online/dsc/disconnsingle.cfm

http://www.xmission.com/~jry/ww/shop/magnetic-switches.html
http://www.xmission.com/~jry/ww/shop/mag-sw-parts_digi-key.html

Any more suggestions about power strips that trip and stay tripped with power fluctuations?

I bought my plug in unit from Amazon:

http://www.amazon.com/TRC-90265-6-012-Shockshield-Portable-Protection/dp/B000XU5MEG/ref=sr_1_fkmr0_1?ie=UTF8&qid=1295623793&sr=8-1-fkmr0

in addition, I noticed that you can get it at my local Home Depot now in FL. for about $15. from Amazon, you can get a white color one, which my Home Depot didn't have.

I like these so much, I put one in the garage for my overhead power reel, as it was plugged in with the Garage Door opener, and not protected by GFCI. Now it's protected, and I can move it if I need it somewhere else.

You might consider this. I use it and when the power goes out even for a second it trips and stays off.

http://www.belkin.com/IWCatProductPage.process?Product_Id=517511

It is made by Belkin and called a "Conserve Switch"

I then use the remote switch to turn everything back on when I want. No cycling to the power.

Hope yall ain't getting annoyed with me digging up all these oldie but not moldy threads. I've been digging, doing some research on the care and feeding of my new baby, a VTA ST-120.

Wasn't aware of the short cycling issue. Just pulled the trigger on a

TRC 26020L-4-001 Shockshield Inline GFCI with 14-Inch Cord

To regurgitate ... the important thing is to get something that's "non-latching". This means you have to manually reset after any power outage or major blip. In this case, that's a good thing.

Can't help but notice some of these tube thingies are kinda expensive. Seems like relatively cheap insurance against some of the bad stuff lurking in the wires ... (boo!)