New caps in C+

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Henz
Mark II
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New caps in C+

Post by Henz » Tue Feb 12, 2019 4:11 pm

Hello, I have a DRG 1984 C+ with all original caps. I'm currently in the middle of recapping. Will I hear an improvement in tone or will it just make it quieter? I'm doing all caps on PSB and the two on the EQ board. Thanks, Jim
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woodbutcher65
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Re: New caps in C+

Post by woodbutcher65 » Tue Feb 12, 2019 11:30 pm

It's going to tighten up the bass response like you won't believe. The flub will be gone.

The amp will sound better in every way.

Hopefully you're getting the caps from Mesa. They're using BMI caps these days and those are among the very best and Mesa's pricing on them is actually almost too good to be true.

DO replace the bias caps. Some people overlook them. Then they have bias problems and red plating tubes not long afterwards.

Henz
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Re: New caps in C+

Post by Henz » Tue Feb 12, 2019 11:56 pm

Thanks for your reply! That's great! That is what i wanted to hear. Yes, I got all caps from Mesa. My amp had 50u 75 vdc for bias.I install 47u 100vdc bias caps. Will that value be ok? I hope. They're already in. Someone told me that when I replace my filter caps that I should also replace my .1 coupling caps on output board since the new caps might throw them outta spec. Was that you? If not, what do you think? I have them on stand by in case i need too. You are a great help. Thanks! Jim
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woodbutcher65
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Re: New caps in C+

Post by woodbutcher65 » Wed Feb 13, 2019 9:33 pm

Yes, going up slightly in value and voltage on the bias caps is fine. It's USUALLY OK to increase voltage or value by up to 50 percent when the cap is in a power supply.

Just don't go down in voltage rating. That's the big rule.

Yes, be prepared to replace the .1 coupling caps. Put in only original Sprague or new CDE orange drops. Not "generic" orange drops, but real ones that these days are made by CDE (Cornell Dubilier Electronics).

The reason for this is that the recapped power supply now puts out higher voltages and it's not uncommon for that to push a 30 year old coupling cap over the edge. The result of this will be a shorted cap and red plating power tubes. If one cap shorts, half the power tubes will red plate. If both caps fail, all power tubes will red plate because they've now lost their bias voltage.

Yes, other brands of coupling caps can be used but they will SLIGHTLY change the tone. For a Mesa, Orange Drops help create the tone we've come to expect from a Mesa amp.

Henz
Mark II
Posts: 105
Joined: Wed May 18, 2016 11:05 pm

Re: New caps in C+

Post by Henz » Thu Feb 14, 2019 12:08 am

Nice to hear from you again. Those .1 caps , a while back, you suggested 715's . Sprague , CDE's. I didn't get those. I got these instead at 600 vdc. I think 200 vdc are the originals. Maybe 400. I just looked at them and i forget. to much on my mind. https://www.tubesandmore.com/products/c ... page=0%2C1 Should i toss these and get the better ones as you suggested? The reviews looked good.That's why I grabbed them. I hope to hear from you. I have plenty to do before i get to the orange drops. Thanks for your time, Jim
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woodbutcher65
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Re: New caps in C+

Post by woodbutcher65 » Thu Feb 14, 2019 11:46 pm

715 is the SERIES IDENTIFIER of a desirable series of Orange Drop caps, not the voltage rating.

Just clarifying that point.

If you put in other caps, I would not suggest tossing them out to replace them. Try them first. Sometimes you will find that the parts that sound best to you are not the traditional selections.

Henz
Mark II
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Joined: Wed May 18, 2016 11:05 pm

Re: New caps in C+

Post by Henz » Fri Feb 15, 2019 12:08 am

Thanks for the reply. 'I'll give em a try. The orange drops that i got from that site do have CDE stamped on them, but anyone can do that. Your point on the 715's is understood my friend. Yep, I made sure that I looked today, 400vdc are in there now originally. Thanx for all of your help. I'll let you know what happens when I hit the power switch when I am finished. Blessings, Jim
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woodbutcher65
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Re: New caps in C+

Post by woodbutcher65 » Fri Feb 15, 2019 6:49 pm

If you got CDE branded orange drops from a reputable retailer, you got genuine orange drops. It'll be fine.

Henz
Mark II
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Joined: Wed May 18, 2016 11:05 pm

Re: New caps in C+

Post by Henz » Sat Feb 16, 2019 12:04 am

Thanks. I'll be changing the two 220u 63vdc caps on the eq board. Do you think that I should bother with the two smaller 10u 63vdc caps on it? When I removed the board from the side of the chassis, both of the 220's (- ) sides are all burnt all around the leads. I wish that I can post a pict. Don't know how yet. But Im assuming that they are shot. Thoughts? Thanks, Jim
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woodbutcher65
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Re: New caps in C+

Post by woodbutcher65 » Sat Feb 16, 2019 10:16 am

Every single electrolytic cap in that amp is now 34 years old. Yes, I'd change them all. There's no reason not to.

If I don't buy a cap direct from Mesa then I buy from Digi-Key or Mouser and pick long life types. If I could get them all the time I'd always put in 10,000 hour, 105c rated caps for everything. Or even higher hours ratings when available, as long as the price doesn't become utterly absurd.

Henz
Mark II
Posts: 105
Joined: Wed May 18, 2016 11:05 pm

Re: New caps in C+

Post by Henz » Sat Feb 16, 2019 1:21 pm

Mesa has them. I wish that I would have seen them before ordering the others. Two of them are 80 cents. S & H is over 7.00. Guess I better get them then every electrolytic cap in that amp will be new.
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lovetoboogie
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Re: New caps in C+

Post by lovetoboogie » Sat Feb 16, 2019 1:56 pm

Wholly unnecessary to replace the .1uf output coupling caps. The PI circuit has a very low plate to cathode swing causing little or no current. All you are left with is the plate voltage at the input of the caps which is a non-issue even after a cap job. The modern polyester film/foil Orange Drops(225p, 418p, 4PS, 6PS series, etc) or the Metalized Polypropylene(715p, 716p series) capacitors are super forgiving in that section of the amp and rarely if ever need to be disturbed. Current and heat cause film capacitor failure. Idle plate voltage does not if it is below the caps rated handling. In the case of original Mallory's or Sprague Orange Drops or the newer CDE ones...they are spec'd for a 100-200% DC overages. Mesa knew all this when they designed the circuit...

I say all this with the utmost respect for everyone's input as far as repairs go. I am particularly intent on keeping older Mesa Boogies Mark Series amps as original as possible except when to do so would impede the performance of the amp. This should be emphasised more so with your IIC+ since so few were produced.

Great info about getting the electrolytics replaced. It's good to do the all the filter stages at one time to rest easy down the road.


75 Mark I PI Section still rockin arenas near you!

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Henz
Mark II
Posts: 105
Joined: Wed May 18, 2016 11:05 pm

Re: New caps in C+

Post by Henz » Sat Feb 16, 2019 9:24 pm

Thanks for the reply. I kinda understand you. What you mentioned with regards to plate voltage, my amps plate voltages at pin 3 of output tube is around 500v. My coupling caps in there now are rated at 400v. Do I need to put 600v caps there ,or am I way off base here? Thanks, Jim
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lovetoboogie
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Re: New caps in C+

Post by lovetoboogie » Sat Feb 16, 2019 10:59 pm

Henz wrote:
Sat Feb 16, 2019 9:24 pm
Thanks for the reply. I kinda understand you. What you mentioned with regards to plate voltage, my amps plate voltages at pin 3 of output tube is around 500v. My coupling caps in there now are rated at 400v. Do I need to put 600v caps there ,or am I way off base here? Thanks, Jim

No, the plate voltage on the PI tube(pin 1 & pin 6 of V5) is not the same as pin 3 on the power tubes. The plates of the Phase Inverter "see" anywhere from 275-350vdc depending on Mark Series amp... If you are seeing 500vdc on the plates(pin3) of the power tubes then you have a 105 Power Transformer. Good stuff!

Henz
Mark II
Posts: 105
Joined: Wed May 18, 2016 11:05 pm

Re: New caps in C+

Post by Henz » Sun Feb 17, 2019 12:10 am

Aah, gotcha . The plates of the PI socket went completely over my head. So you still think that I shud leave those caps alone? I took a close look at one tonight while installing new caps on EQ board and one had a little spot where the orange coating was missing. About the size of a pin head. Thanks to you and WoodButcher65 for your help. Jim
MKIIC+
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4x12 Recto Cab w/ Eminence and V30's
Home made 2x12 half open cab w/ Eminence and V30's
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