vintage 1265x Fisher Capacitors 1979

[AnInstant]

Greetings from a newbie and a basic parts re-placer. I have brought out my Fisher 1265x
that I bought new in 1979, used twice in TN, and then stored as I moved around in the Navy.

Should I replace the aluminum caps w/ wet electolytic with solid electolytic caps or can I use, and I want to use, Tantalum capacitors?????

and I would consider trading this to a board member of good standing for a current
tesoro model...just write

thanks john, in sacramento
'
all capacitor advice read, and the names/models; and modern design recommendations would be important to me in choosing replacements for
the older, and I suspect, dried out electrolyte models fisher chose in 1979. Thanks in advance/

[ivconic]

1265 is excellent machine, i wouldn't ever want to exchange it for something else.
Replacing caps is good idea, in case they dried.
But if device was kept protected in a dry place; than huge chance is that most of caps are still in a good shape.
Have you tried to insert batteries and switch it ON?
Maybe there is no need to replace caps yet?

[AnInstant]

thanks

Thanks for writing a great reply. Before I posted here for the first time I read plenty of posts (many many were yours) at Geotech looking for guidance on replacements in capacitors. Your attention to my post gives me hope, and I can only be a happy sponge to the knowledge of circuits you bring here. Thanks!!



I feel certain (but do not know) that the Capacitors in my detector have **aged out and dried up** I have researched plenty of online opinion and comment on Tantalum caps in circuit designs, and feel pretty certain I can use them as long as I observe polarity and increase the rated voltages when using them as direct replacements for aluminum capacitors. Yet your opinion and expertise comment would make me at ease.


My parts sources have some wet slug tantalum caps, but the more modern dry Tantalum
capacitors seem the very best choices

all help appreciated.

thanks john

[Carl-NC]

I would test the detector, and if it seems to be working OK then leave the caps alone. Most likely they are fine. White's gets a lot of 30-40 year old units sent for repair, and e-caps are rarely the problem.

[ivconic]

I would test the detector, and if it seems to be working OK then leave the caps alone. Most likely they are fine. White's gets a lot of 30-40 year old units sent for repair, and e-caps are rarely the problem.

That's true.
Common problem at vintages could be mechanical; dust in a potentiometers, cracks, shorts, rust...etc..etc..
If 1265 shows some problematic behavior; than first to check would be mechanical parts, such are pots and switches.
Fisher already implemented tantalums on places where those are necessary. Others, as ordinary elco caps are just fine to stay the same kind.
...
There is certain "in circuit cap tester" device, which saves time and job when testing and replacing suspicious capacitors. Good to have such one in workshop.
But, at metal detectors; as battery operated devices (low DC voltages), capacitors usually do have longer life than
capacitors at devices which are supplied through AC network and/or operating on higher supply voltages.

[AnInstant]

Thanks for the good advice given to me, a beginner.
I am glad for this forum, and feel kinda of left out because I will likely, never build my own detector or coil. Yet is good to read the combined knowledge that is upfront here.


regards john, who will take the advice given.


THNX

[ivconic]

Speaking of "in circuit cap tester", i found this to be interesting:

http://members.shaw.ca/swstuff/esrmeter.html

[ivconic]

Eh!
I missed this: "...Tests electrolytic capacitors > 1uf in circuit..."


Not covering most of elco's values there...

[Sean_Goddard]

If you DO replace any caps with "Tants" ONLY in th power supply as any others may be making use of the low ESR (Effective Series Resistance) of the wet type Ecaps and Tants are not exactly known for having good ESR's.

Best advice? Leave well alone unless you have a problem.. Remember the military adage.."If it ain't broke, don't fix it"!

[Vortxrex]

I would test the detector, and if it seems to be working OK then leave the caps alone. Most likely they are fine. White's gets a lot of 30-40 year old units sent for repair, and e-caps are rarely the problem.

I have fixed quite a few of those old White's from the 1960's & the problem is mostly related to the battery packs/contacts.

[ivconic]

I have fixed quite a few of those old White's from the 1960's & the problem is mostly related to the battery packs/contacts.

You don't say!
The other day i bought Cscope1220B in perfect condition... except those damn battery holders, at which spring contacts are completely destroyed by acid.
I bought new ones (made in China), tried to use them and after few tries also tossed them to garbage!
(despite the fact that those are new and shiny - still losing contacts on slightest move)
So now i am using external accus 12V+6V with it... until i find more proper solution.
(was thinking to make dc/dc tripler and only one 6v accu which will perfectly fit battery compartment at 1220B).
The rest of Cscope (machine, enclosure, pots, switches, connectors) are in perfect shape.
Like it was never used. Machine is functioning also perfect.
So, only damn battery holders suffered through all those years...

[turtlebowl]

Nice link and tester. Thanks Ivconicc.

[satdaveuk]

You don't say!
The other day i bought Cscope1220B in perfect condition... except those damn battery holders, at which spring contacts are completely destroyed by acid.
I bought new ones (made in China), tried to use them and after few tries also tossed them to garbage!
(despite the fact that those are new and shiny - still losing contacts on slightest move)
So now i am using external accus 12V+6V with it... until i find more proper solution.
(was thinking to make dc/dc tripler and only one 6v accu which will perfectly fit battery compartment at 1220B).
The rest of Cscope (machine, enclosure, pots, switches, connectors) are in perfect shape.
Like it was never used. Machine is functioning also perfect.
So, only damn battery holders suffered through all those years...

Hi
I got good quality replacment battery holders for the 1265 at farnell, they stock various brands go to the most exspensive ones you cant go wrong.
Far as the on/off volume control which is a 10k lin pot had to order from thiland in pk of 5, perfect fit and good quality build.
Regards

[nittany1]

Blue ESR Meter testing 400V .1µF cap

If you want to check the caps in circuit, as long as they're not parallel, most ESR meters will work just fine. I have the Blue ESR meter but there are several on the market that will do the same thing. You have to know what ESR a cap of the same specification will have when brand new. In the picture I'm testing a cap that I'm going to put into an vacuum tube tester and an old Heathkit integrated tube amplifier from 1959, I bought a half dozen of them because it's a common high voltage cap that goes into a lot of things.

When caps age and dry out their ESR drifts way up in value like an old resistor, plus when the caps age they get leaky or can't hold anything at all.

Note: the ESR meter has red and black leads but it doesn't matter. It uses a few millivolts of AC power and doesn't have a polarity, you can use whichever lead you want on either side of the cap.

[Pennypacker]

I know this is an old thread, but I myself would replace the electrolytic capacitors on a machine from 1979.

Any electrolytic or 10 years older could potentially fail.
Kind of like 35 year old tires on a car.