Welcome, Guest. Please login or register.

January 22, 2022, 09:40:05 PM

Login with username, password and session length

 

Author Topic: To re-cap or not to re-cap??  (Read 3193 times)

Anomaly

  • Regular
  • **
  • Posts: 11
  • Chip Points: 0
    • View Profile
To re-cap or not to re-cap??
« on: June 29, 2015, 01:04:11 PM »
I have a mid 80's Randall head, and this amp is getting quite old, but it has never failed me yet and sounds as good as it always has. Thing is I'm worried about the caps going, and killing the amp. It doesn't have any real symptoms of dying filter capacitors, but i'm wondering if replacing them is necessary and the smart decision or not?? I know it is common for tube amps to need a re-cap after about 20 years or so and I have had caps in a couple Mesa's fail on me, but tube amps run much hotter voltages. Is this repair just as common in old SS amps?

Do I recap or just leave as is, since it has no obvious symptoms? I do notice idle hum, but that has been the case with every RG i've used... and it's just a quiet background hum. Also... If I do replace them, is it going to change the amps tone in any way? Positive or negative, and how so??

LateDev

  • Regular
  • **
  • Posts: 42
  • Chip Points: 1
    • View Profile
Re: To re-cap or not to re-cap??
« Reply #1 on: June 29, 2015, 06:19:35 PM »
 I have never seen the need to replace any cap. It all depends on what caps you are talking about, but I have never seen a cap blow an amp up by itself, it is usually a symptom of the fault, rather than the cause.

DrGonz78

  • Legendary
  • ******
  • Posts: 575
  • Chip Points: 74
    • View Profile
Re: To re-cap or not to re-cap??
« Reply #2 on: June 30, 2015, 05:22:28 AM »
Just yesterday I was tearing apart an old tube amp radio for a future project. The thing is from 1947 and I was clipping out some of the old electrolytic caps. Most of the time I will take the old cap and shake it to hear if something is jostling around inside. Dried up completely in those cases, but this cap did not jostle inside. This got me curious! Took out my very trusting Fluke meter and set it to read the capacitance. The cap is a 16uf 500v rating and measuring with the Fluke it read exactly 16uf on the dot. That is impressive to me as the cap is nearly 70 years old. I then did an ESR reading and it measured 1.2, which is pretty darn good! I am sure that applying high voltage to this thing might not yield such equally great results. Although I am still curious... Will let you know if I bored enough to find out if the cap still works. lol.

Anyway more on point to the OP's question. You seem to know that the hum in the RG amps is pretty normal and replacing those caps probably won't get rid of the already known hum. You need to get out the voltmeter and measure for AC ripple to see if the hum is caused by leaky filter caps. That is the only true way to determine if you have AC ripple hum from the caps. If the caps are still good and you replace them with new caps there will probably be no positive or negative, it will probably just be the same. However, if you replace the caps and make a mistake then that would be a negative.

Just to add one last thing. I had a RG80 from 1986 that I bought to repair. The guy brings it over to my house and we plug it in the guest room of my house. The thing was humming hard and noisy as hell. Paid him the money and went to work. My Mom's boyfriend calls me later and says hey man that amp sound killer!! I was like killer as in kill your ears? No man it sounds great!! So I get home we go in my shop and sure enough it is quiet as mouse with that tiny bit of hum they all have. I then brought the amp to jam at a friends house to test it out further. This time the hum and noise was full boar again. Brought it back home to the shop plugged it in and no hum. Changed out the filter caps and tried it out again in those same places where it was humming. No hum. So for some reason that particular amp had me stumped completely. Actually that whole story still amazes me today.
“A person who never made a mistake never tried anything new.” -Albert Einstein

Anomaly

  • Regular
  • **
  • Posts: 11
  • Chip Points: 0
    • View Profile
Re: To re-cap or not to re-cap??
« Reply #3 on: July 14, 2015, 03:48:14 PM »
Ya, that is weird.  :o

Ya know, I think this rg100es sounds so good. Even at band volumes it's tight and very warm sounding for solid state especially with a boost in front. Recently I got one of the newer rg3003h heads and thought because it's a new version of the old 80's Randall's that it would at least be good for a backup??... nope not really..., it's just not as toneful as the old version. It's got a more modern feel and more gain, but there's some serious mojo in the 80's Randall's that they have not captured with the new RG series.

The rg80es, rg100es, rg100ht are almost like solid state versions of a jcm800, but with a certain unique quality to the mid range. It's been the heart of my tone for 10 years now. I guess that's why I'm thinking of putting in new filter caps?? cause I don't want it to fail on me.

J M Fahey

  • SSGuitar Global Mod
  • Legendary
  • ****
  • Posts: 4142
  • Chip Points: 429
    • View Profile
Re: To re-cap or not to re-cap??
« Reply #4 on: July 14, 2015, 07:00:24 PM »
Don't fix what's not broken.