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[FdB]

As the Vintage Portable Amplifier project here still slowly edges towards completion (I’ve two speaker grille assemblies to create / construct for two re-cabbed Mouse amplifiers and an 8-position rotary switch to install in a Roland Cube Street)… here are a few tips, tricks and hints that I’d like to share.

(1). Considering the 40+ years that most of the original paper-coned speakers have endured and the fact that direct replacements are difficult (if not impossible) to find… here are two approaches for “treatment” of some of these old original speakers have been used here.

    [a]. Visaton (Germany) LTS 50 speaker treatment. A brush-on coating that “stiffens” seals and preserves the integrity of the paper speaker cones from the “paper-turns-to-dust” scenario of these older speakers. Sure, it affects the overall tone of the speaker after a coat or two. (It tightens and increases treble end while somewhat reducing bass.) But just try to find an 8” 2Ω speaker for a Mouse or Maxi-Mouse amp. Or… spend nearly $40.00 for a Pignose replacement speaker - direct from Pignose.

    [b.] If I use BOLD on this "b" everything after this would have been in BOLD type. So...

    [c]. And here’s a weird one… used primarily for the speaker surrounds - where the speaker cone is attached to the outer frame of the speaker. *Also used on rips and tears in the cones themselves (before the above mentioned LTS 50 treatment). Some might be more accustomed to the old fingernail-polish approach for rips & tears?

Using “Brush-On” Electrical Tape, sufficiently diluted with acetone in a separate dish to enable better “brush-ability” - I have painted some of the old decaying speaker surrounds with this mixture. As the added acetone evaporates from the applied mixture, it then leaves the flexibility of the rubberized, Brush-On Electrical tape. Time will tell if it eventually gets brittle?

(2). Potentiometer cleaning. Never completely satisfied with the performance of De-Oxit or other versions of aerosol electronic cleaners for cleaning pots - they always seem to leave some greasy, oily residue which I believe adds more dust & dirt build up gunk (over time) inside the pots after cleaning… also considering that their use doesn’t seem to always throughly clean the pots anyway? I tried something different.

Recent acquisition of a Peavey / Special 212 amplifier here (with 18 mini-pots and 6 push buttons) led me to try something that would allow better access into the pots. 91% alcohol injected into the pots via a hypodermic needle. Irrigating and flushing each pot while turning each one individually, back and forth repeatedly… led to absolute zero “scratchy” pot noise. In fact - ZERO noise. (Compressed air afterwards, assured total evacuation of any possibly remaining alcohol.) So yesterday… I went back and cleaned (only) eight other portable amps in this manner. (And now I’ve a few guitars and other portable amps to use this same method on.) *Also used alcohol on a pipe cleaner (twice-doubled) to interior clean all 1/4” input /output jacks.

Again - all perhaps unorthodox methods… and I welcome possible detractors.
Have better approaches? Do please share.

AND (as per usual) follow the above methods at your own risk.

[Protools5LEGuy]

When I clean pro stuff like EV ZLX 15P https://www.thomann.de/es/ev_zlx_15p.htm I use first air compressor softly to remove most dust. Then I clean woofers with a lightly watered cloth.

In some cases like 15 years walking NEXO PS-15 or Touring systems I have applied latex to the paper, but it changes lightly the sound, because membraine "weight" more than original, but make them lightly waterproof and moisture rejector, and under normal use it only make them gain low end.

[Protools5LEGuy]

20 years ago we only had "3in1" (3 en 1) electrical contact cleaner

For Potenciometers (Pots) we use 3 kind of "CRC".

One than cleans and "eat" (disolve) most grime

One that barely cleans, but keep the carbon track of the pot "wet" ensuring contact.

Other one that was between the others

[Protools5LEGuy]

You have to understand what is fisically a pot.

What the cursor do when to move it.

It is a carbon track that makes wider and widest at the end.

When you clean and clean and clean, you end "eating" that carbon track.

If the carbon track has been ruined, best to put some new japanese metalic pots.

You want the carbon track to have some "dust" (or be wet) to fill the gaps between contacts an ensure best conductivity.
 

[Protools5LEGuy]

In the end, have rightly lubricated an pot is a pro task.

https://www.amazon.es/stores/node/7034080031

On lightning, moving head wants littium (white) lubricant on its step by step motors.

[FdB]

Thanks Protools5LEGuy.

Appreciate the comments and insights. Have used De-Oxit and other electronics cleaners almost exclusively in the past. But, on the miniature pots and especially on the much older vintage portable amplifiers… the alcohol and syringe method seems warranted… at least for a one-time big cleaning effort.

I also additionally considered just a little bit of the De-Oxit (and similar cleaners with some lubricant) applied, after the alcohol method - to reduce friction and wear on the pots. I still do not like the oily residue left by such cleaners on circuit boards and ofen use denatured alcohol for that cleaning. Dust covers and yearly, compressed air blow-outs need be employed.

Hopefully, no pots here will need eventual replacement - but your Japanese pot suggestion will be considered as is necessary.

The Visaton LTS 50 speaker treatment is much like your latex. The LTS 50 seems like somewhat-diluted Elmer’s Glue or some other aliphatic resin-based compound. Yet, it may in fact be latex? And I will have to recheck my ears for that low-end increase. Seems that treatment would somewhat restrict cone movement / flexibility and thusly reduce bottom-end bass response… but I may be mistaken.

40+ year-old speakers and pots may need more than a traditional & typical approach?

[Protools5LEGuy]

I still do not like the oily residue left by such cleaners on circuit boards and ofen use denatured alcohol for that cleaning. Dust covers and yearly, compressed air blow-outs need be employed.

If you dont like that oily residue is a bad thing. "Wet" pots have longer lifespan. "Eternal" pots are those that are sealed. 

The Visaton LTS 50 speaker treatment is much like your latex. The LTS 50 seems like somewhat-diluted Elmer’s Glue or some other aliphatic resin-based compound. Yet, it may in fact be latex? And I will have to recheck my ears for that low-end increase. Seems that treatment would somewhat restrict cone movement / flexibility and thusly reduce bottom-end bass response… but I may be mistaken.

When you hit with the nail the paper, on an untreated cone you hear "Click click". With the treated you hear "clock clock". It gains body and looses some high frequencies. On a guitar amp you usually prefer that. Treble is not needed on a woofer cone.

[Protools5LEGuy]

When you hit with the nail the paper, on an untreated cone you hear "Click click". With the treated you hear "clock clock". It gains body and looses some high frequencies. On a guitar amp you usually prefer that. Treble is not needed on a woofer cone.

Just like when you tune a snare, it is subtle, but there is different pitch on every screw.

[FdB]

Well, it seems that there are possibly injectable liquid forms of DeoxIT that could be used for the mini-pots - and after the thorough flushing of 25 year-old & older pots (in the case of the vintage portable amps)… with more efficiency and without the usual waste normally attributed to the attempted use of the aerosol cans into such small pot openings. So… a good thorough flush with injected alcohol followed with a small amount of injected liquid DeoxIT afterwards for just that little bit of lubrication… and without getting it everywhere and all over everything else. AND, maybe not really all that expensive when you consider how long it might actually last as an injectable liquid. I can accept this as an adjunct to the alcohol flush for the older pots when attempting renewal of older amplifiers.

Concerning the bass response question… in regards to speaker treatments reducing or increasing bass response. This was primarily concerning the vintage portable amps and their common 5” and 8” full-range speakers (bass, mids and treble response all-in-one).

I’ve two 8 inch, identical speakers - one treated and one un-treated. Eventually, I’ll use both in the same amp to test & record both individually and under the same conditions. Then, compare the curves from those recordings to arrive at a hopefully definitive answer. If such a difference amounts to really all that much.

Enjoyed the snare drum analogy - and now applied to a bass drum head… does the pitch / tone of a tightened bass drum not decrease the amount of bass as the head is tightened?

*And, of possible interest concerning your EV ZLX15P powered speakers: www.youtube.com/watch?v=XqIUkr7JuDM

[Syntho]

I've gone through I don't know how many cans of deoxit in my time. I always have a couple on hand. The last thing I cleaned was actually some HiFi equipment from the 80s. Cleaned up all the pots, switches and buttons and it works perfectly now.

[Syntho]

I’ve switched over my contact cleaner from deoxit of various types to MG Chemicals 409B Electrosolve Zero Residue Electronic Contact Cleaner. Bought a big $20 can of it and I couldn’t be happier. This stuff doesn’t leave an oily film like deoxit. Deoxit is still good for some things where it’s in a closed/sealed space (so not susceptible to dust) and needs a bit of lube, but this 409B is just fantastic. No residue at all as advertised.

The big can I ordered cleaned every single pot and switch on a 24ch mixer and I’ve got probably 85% of it left. Cant recommend it enough. For really careful cleaning, use this stuff plus some lube of your choice and skip deoxit altogether.