parallel silver mica caps opinions please

[Justin Thomas]

Agreed. I reckon quality/durability/whatever you call it is at least SOMEWHAT dependent on how many fingers are in the pie?

I can say I've had very few warranty failures in my life, and with some TLC, very few failures of anything. Most of the actual failures or damage happen due to improper care, handling, or maintenance by the "middlemen." I aim usually for middle of the road, not the cheapest (quality, not price) not the highest, and I do okay. Specifically for gear, I figure if an amp's survived 40 years, it'll do me good.

Perhaps the real issue (it is for me, anyway) is NOT that This or That construction practice is more reliable than the other, but that This method <I> can repair myself, and That one I cannot. That's how I look at it, being poor... So I buy old-style construction amps.

But I do live by this rule: the more moving parts there are, the more likely it is to break and and cost more to fix.

Justin

[musicamex]

What a fantastic direction this topic has taken. Mr fahey, you show how engineers are really constrained by the bottom line and maybe have to or have forgotten the small design features for longevity that wouldn't add much at all to the cost. Your post was worthy of the TNS. THANKS AMIGO!

The jack i replaced was already on a finger projecting from the main board. Had that finger been seperate from the board, LIKE THE XLR JACK RIGHT UNDER IT and like jacks on much cheaper amps i've fixed, the tiny sub board would have come out easier and the amp might not have fallen into the dnr box. The difference for the one part most likely to fail being easier to replace is 3 shory flying leads and being mounted seperate on the chassis. It really didnt even need a board! Granted, i found a way, but through guerilla warfare and stubbornness. this came up as a comment on pcb boards being suitable in tube amps. If the controls, jacks and tube sockets are not mounted to the board they have a higher survival chance.

I really enjoy this site. There is allot of grey matter here and it certainly stimulates mine. The ideas and tips save me time and lead me to new solutions. I wish i had more cyber time to fully appreciate what is here.

[musicamex]

I figure if an amp's survived 40 years, it'll do me good. QUOTE

That fits say the original TWIN REVERB F series. Easy to fix and diagnose with minimal tools and observation. Like a car from that era. The reissue, we will have to wait and see. (i have both, the older by design, the newer as a trade in). Like my toyota corolla, it it super reliable, but it isnt like my old ford pickups that i fixed many times by the side of the road. When a new car dies it takes more than " spark?, fuel? To usually figure out the problem. I KNOW we need technology to give modern society more years b4 the resources are depleted and we have to mine the dumps for recyclables. But an old fart guy who likes to fix things, especially when they might have a few or several more years in them, sees less component based repairable architecture and more disposable "use it till it fails and then get the next one".

A positive twist is this......The Royal Data Throne, Tiny Circuit Board Art Toilet For Dumping Data

And my friend ,among other artists Art of Marion Martinez

[J M Fahey]

Expected failure rate is studied and is calculated as a normal part of production.

Only problem is that it is quite complex (computers help on that) and , of course, you need reliabla data on parts you use ... and that often isn't available, so you must do some on-house testing, and for a long time.

For small factories or new products that's not possible, so a lot of "seat of the pants" reckoning is applied.

Now for "mature" Industries, which have a considerable workforce and have been doing basically the same for a long time, think cars, air conditioning, printers (Epson, HP) , conventional cameras (Pentax/Nikon/Canon) , fridges and freezers, guns, etc. , they have the reliable (often self collected) data and the $$/mind power to calculate and use it.

Specially cars, which are expensive, serviceable, sold by the Millions and can cause at least inconvenience and often damage or death, have honed this to an elaborate art.

The basic calculation is called MTBF (mean time between failures) and they can predict it very well.

By the way, it's the drive behind so current "recalls" which sometimes look incredible, as in "6 million cars recalled because of some obscure problem about which almost nobody complained?"

But I bet they calculated failure percentage, possible loss when sued , and try to solve it before the bubble bursts.

Mean time between failures - Wikipedia, the free encyclopedia

Wiki explains it.

The basic concept (what matters to us) is clearly shown, the graph shows stuff actually being repaired, then it gets Math thick (no problem, we won't calculate it, mainly because of lack of data) , but one important line explains DNR policy:

Mean time between failures (MTBF) describes the expected time between two failures for a repairable system, while mean time to failure (MTTF) denotes the expected time to failure for a non-repairable system.

As you see, non repairable is "just one special case" and is being given thought by the Factory, simply that with low production cost and high repair cost, after a certain break point it becomes cheaper to replace.

Yes, even for something as cheap or simple such as a 10 cent resistor ... simply because a Tech will cost them at least 25 to 40 bucks to replace it.

So by definition, anything below $100 street cost becomes iffy; anything below $50 is simply not repairable, for strictly economical reasons.

That said, if somebody can get a bunch of same product, same failure, he can still repair it if done in batches ... the economics behind "refurbishing".

I once had a similar case: Argentina's Marshall importer, Import Music , sold a ton of JCM900 and Valvestates ... which eventually started to fail .
User abuse certainly didn't help.

Not being in USA/UK/EU/Canada with well stocked Marshall warehouses and cheap overland Mail but behind a very messy Customs barrier, 5000 miles away requiring expensive Air Delivery for anything, they met standard servicing problems with a few Tech school kids working for McD salaries and buying generic parts over the counter.

Many parts were not NASA quality but not available over the counter either, also some amps took longer than expected, so they started cannibalizing new ones for parts, even full PCBs or transformers, or offering full exchange.

They ended up with a back room full of mint looking but not working amps, for one reason or another.

When it started to hurt, they asked for a solution.
Of course they wanted to pay as little as possible.

To make it work for them but also for me, I told them that I would only work in batches ... and we agreed on that.

Lots of around 50 VS8080 which were very popular, were repaired in a couple days, for a fixed price of around $30 each.

Consider that the mighty Dollar buys 2X or 3X here as much as it does in USA.

I worked in their huge warehouse, they provided a couple kids to pull chassis, knobs, jack and pot nuts, etc. , and reassemble afterwards.

I did the actual diagnostic/repair which after the first 10 became almost automatic, same problems started repeating: dead power transistors or failed switches and pots, with the occasional cracked PCB jack.

Some took less than 5 minutes, none more than 20 or 30 minutes.

Under those circumstances Service still is justified, and as said before, I'm certain refurbishers work that way (such as repairing, say, 100 Notebooks or TVs or whatever in a single batch) but if you get a random product, with a random failure, where just disassembly and later reassembly amounts to 30 minutes to 1 hour ... and the Tech must get his mind into it .... cheap servicing becomes impossible.

EDIT: hey !!! just checked and LOVED: http://www.pinktieproart.com/Pages/A...nMartinez.aspx

[mhuss]

The local township has "e-waste" recycling days where the locals can bring electronics to dispose of (these are no longer allowed in the regular trash stream.) They fill tractor trailers with old TVs, computers, stereos, etc. Many are still working but no longer wanted. At least old guitar amps don't become obsolete in that way. However, I wonder how many old Champs etc. end up in one of these nationwide.

[Justin Thomas]

Luckily, I think Fleabay & Craigslist have put a stop to most of the vintage amps going in the trash... and also sadly inflated the prices so ridiculously they probably sit in the attic/basement "collecting value." We have an electronics retailer in town that has a drive-up dumpster to throw it in, open 24/7/365. They don't emcourage driving around back, but they got tired of me bringing my clippings of used desoldering braid and dissected e-caps and blown-up tubes. That, and I never BUY anything. I think they hope I'll look for a replacement whatever it is that a
I'm recycling. Show mecthe hand-wired tube guitar amps and maybe we'll talk.

Justin

[Chuck H]

A few months ago I pulled one of these from a pile at our local dump. Removing the back cover I found all the original tubes, the original power cord, owners manual and sales receipt. Currently residing in a closet, fixing it up is still on my "I'll get to it but it's not a priority" list.

[Justin Thomas]

I'm guessing the tubes are worth the price of dumpster diving is THAT one...
Like my pre-Berlin Wall Siemens projector. I just wish I'd checked the internet BEFORE I took it apart...

Justin

[g1]

EDIT: hey !!! just checked and LOVED: Art of Marion Martinez

Yes, they are very nice. The cornfield one appears to be 3D. There is a second page:
Art of Marion Martinez 2

[musicamex]

This just keeps getting better! And l'm glad some of you checked out Marion Martinez. I used to live near her many years ago. I cant look at scrap boards or parts the same way anymore. I now have a growing pile of salvage with art potential for when us repair guys get a little more free time.😕

[Tom Phillips]

I like the "circuits as art" done by the late Jim Williams. Following is a link displaying some examples. IIRC all of the "art" shown is functional circuitry.
Jim Williams: The light side and classic electronics art sculptures | EDN

[TimmyP1955]

When it's time to beta test, a manufacture should send a batch to St. Louis, and a batch to San Juan. Back in the early 80s-90s when I was in the hi-fi business, the first in-quantity new product failures were most always in those two cities.

[musicamex]

When it's time to beta test, a manufacture should send a batch to St. Louis, and a batch to San Juan. Back in the early 80s-90s when I was in the hi-fi business, the first in-quantity new product failures were most always in those two cities.

Why do you think that was? I can guess San Juan could have been power grid related like here and coastal climate related like here, but St Louis has me scratching my head.

I wonder if sending out a few new products to repair shops might help making common repairs cost effective. I always could see leo fender's experience as a repair guy show up in his designs. That began to change after CBS took over.

[Enzo]

Beta tests means early production, to see what problems might remain to be sorted. I'd expect wherever you beta a new product, that will be where a higher percentage of problems appear. They then adjust the product and the rest of the production run is more successful. No need to blame the weather or anything.