Valve amp - capacitor question

slimecity

Super Member
Hi there - I have bought a NZ built 10W valve amp that runs off EF86 and ECL86. Its really nice.

It has a hum in one channel that moves when to the other channel when I swap the pair of ECL86 to the other channel. So I guess I need new outputs.

Someone before me upgraded and replaced most of the resistors. The electro caps have all been replaced too. However please see what I assume are early version ceramics. Any stability/audio quality views on replacing all of these also? If so, what with?

Cheers!

20180206_133928.jpg
 
if you're referring to the 4 beige "caps", they are not usually ceramics which are thin disks
with their connecting wires flat on both sides.

can't read the values, the vendor, the % marking, or any other stenciling that might
indicate the materiels used. (things like MKP, MKT, etc).

also ceramics are also usually low values, and some c0g ceramics are actually OK
for use in audio circuits.

no need to replace until you find out what caps these are, they may very well be
"good" caps
 
if you're referring to the 4 beige "caps", they are not usually ceramics which are thin disks
with their connecting wires flat on both sides.

can't read the values, the vendor, the % marking, or any other stenciling that might
indicate the materiels used. (things like MKP, MKT, etc).

also ceramics are also usually low values, and some c0g ceramics are actually OK
for use in audio circuits.

no need to replace until you find out what caps these are, they may very well be
"good" caps[/QUO

It's probably something ok at least, but yeah don't really like ceramics or Tantlums and all that junk despite some great stuff been built with it. I think it imparts more hash and fizz closer to something icy and transistory. dull and flat smooth anything film&foil or maybe Polyester. You want bright sharp and Hair and stuff definitely Polypropylene MKP anything Metallized that stuff.
 
looks like Mullard "mustard" caps. Its some flavor of film cap that lasts just about forever. Polyester or polystyrene probably. Pollywannacracker? Something like that.

I'd leave them be honestly.
 
looks like Mullard "mustard" caps. Its some flavor of film cap that lasts just about forever. Polyester or polystyrene probably. Pollywannacracker? Something like that.

I'd leave them be honestly.

Was my first thought but I know quite a few look a likes. I'd still change em for polypropylene probably. some 715p's would sound good.
 
looks like Mullard "mustard" caps. Its some flavor of film cap that lasts just about forever. Polyester or polystyrene probably. Pollywannacracker? Something like that.

I'd leave them be honestly.
Sweet - thanks - that sounds good to me.

Next question - is there an easy way to clean inside valve sockets? The sockets for the power tubes are looking a bit blackened - if theres a way to get in there to clean them, that would be good. I have contact cleaner but suspect a bit of a brush with something as well would be good.
 
I just don't think there's that much magic in a 20-50 year old capacitor. Yeah some that still sound good and are ok but a lot new stuff too that also sounds great.
 
Sweet - thanks - that sounds good to me.

Next question - is there an easy way to clean inside valve sockets? The sockets for the power tubes are looking a bit blackened - if theres a way to get in there to clean them, that would be good. I have contact cleaner but suspect a bit of a brush with something as well would be good.

Carb jet brush set?
 
Sweet - thanks - that sounds good to me.

Next question - is there an easy way to clean inside valve sockets? The sockets for the power tubes are looking a bit blackened - if theres a way to get in there to clean them, that would be good. I have contact cleaner but suspect a bit of a brush with something as well would be good.

DeOxit is good for that. What I do, is spray some of it on a cotton swab and clean the inside of the socket. If the cotton swab is too big, like for most noval (9 pin) sockets, spray a little into each pin/socket. Try not to overdo it though, can get a bit messy.
If all fails, perhaps a new socket, but that would require a lot of work, desoldering and resoldering though.
As to those mustard caps, as has already been pointed out, they usually remain good for just about eternity. Only replace them if there is an issue with one.
 
what you went with on the electro side too. Must be the Plague again with China and Taiwan, some Xunda's from like 15-16years ago sound better than some pretty new Lelon's lol. Pretty bad lol
 
And like have always advised and improvement in ESR since before my time, yet literally just about everything going or getting high sounds cooler.
 
I just don't think there's that much magic in a 20-50 year old capacitor
I don't buy into magic in any cap. I'm just not terribly motivated to change parts that are electrically fine, especially when they're a pain in the neck to replace, and these definitely look annoying.

For small tubes, those inter-dental brushes also work well. Octals do fine with smaller pipe cleaners.
 
Concur with knockbill. Oxy Torch tip cleaning brushes work well. And they are cheap in the states. Find a Welding supply house and ask for a set of tip cleaners.
 
Hi there - I have bought a NZ built 10W valve amp that runs off EF86 and ECL86. Its really nice.

It has a hum in one channel that moves when to the other channel when I swap the pair of ECL86 to the other channel. So I guess I need new outputs.

Someone before me upgraded and replaced most of the resistors. The electro caps have all been replaced too. However please see what I assume are early version ceramics. Any stability/audio quality views on replacing all of these also? If so, what with?

Cheers!

View attachment 1107448
As many say those Mustard caps maybe good so not necessary to change. But recently i had an experience with some "ceracaps" in a Scott 222. I left them in while rebuilding the Power supply on the amp as they seem to be ok. But, later changed them out for some orange drops. When i cut out the ceracaps they did test good on my cap tester but the OD, made a positive change in the sound quality. The sound was more dynamic and sound stage improved. So, if you think the sound is too soft in your amp you might consider changing the coupling caps between tube stages.
 
I forgot to add that the resistors that you show in the photo looks like metal oxide type. Those are perfect in the power supply and work well in other areas but one would usually put in carbon comp or film type resistors in the preamp stages. Carbon film or metal film is less humbug than carbon comp.
 
So, if you think the sound is too soft in your amp you might consider changing the coupling caps between tube stages
Cheers for that - I'd first need to identify which ones these are in the circuit - if this is based on a Mullard 10-10 amp I'd need to find that circuit., your suggestion makes sense as it sounds similar to a solid state mod I would usually do.

I forgot to add that the resistors that you show in the photo looks like metal oxide type

Pretty sure these resistors are all standard modern carbon types.

Cheers
 
Cheers for that - I'd first need to identify which ones these are in the circuit - if this is based on a Mullard 10-10 amp I'd need to find that circuit., your suggestion makes sense as it sounds similar to a solid state mod I would usually do.



Pretty sure these resistors are all standard modern carbon types.

Cheers
The picture is not that clear but they appear too big. You would be using 1/2 watt in the tone controls and preamp sections. Most half watters are around 10mm mas or menos. A way to tell is that metal ox resistors have a rougher surface whereas carbon and metal film are usually smooth from an expoxy coating. Carbon comp are almost all brown.
 
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