Tech Help Needed RE: DC-3

[Boogie Bill]

This is my first post. I am so glad I found this board. I have five Boogie amps, and I have been using Boogies exclusively for about 12 years. I hope to able to contribute my knowledge and experiece with Boogies, but for my first post, I got a problem; and I need your help.

I have a DC-3 112 combo--the model with the three toggle switches on the front. I have had it to two techs and spent over $300 trying to get it fixed. Here's what's happening:

The major symptom: it gets HOT! And I mean, too hot to touch the chassis. I'm playing it on 4, not 10, by the way. It appeared to me that one of the power tubes in an inner socket was running too hot. The tubes were GT-EL84s and the orange labelling ink turned brown within a few hours of playing--a sure sign of something being amiss. I know EL84s run a little hot--that's part of their charm; but this is running way hotter than my Class A Maverick 212.

After getting burned even worse by the first tech, who simply replaced the tubes and put in a fan (without permission! IDIOT!), I finally took the amp back to an old friend, a tech about 200 miles away.

And basically, they couldn't find anything wrong with it--other than one bad tube, in the same socket as before--so in went another new set of tubes. I played it for a few minutes in the shop and it sounded great.

First gig out with it, and it sounds great for about 20 minutes, and then gets progressively worse through a 45 minute set. Chassis again is too hot to touch. By the end of the set, the guitar has no sustain at all, and notes are being clipped short.

Okay, so I am going to be taking it back to my friend this week, and he's not happy that it is coming back, but he will dig into it.

Does anyone have any experience with something like this? Is there any direction I should be pointing him in?

Thanks in advance.

 

[Monsta-Tone]

Hey Bill,

Welcome aboard.

1. The DC-3 will get extremely hot. Most guys here use a fan and don't place them too close to a wall.

I would do this for starters.


2. Next, if you have to replace 1 power tube, replace 2. They are Push-Pull in this amp and if one of the tubes in the 2 pairs fails, then both will eventually fail.

A lot of times, the tube that is failing is not the one suspected. I have seen 6L6's & EL34's start failing and take the other tube in the pair completely out, while the original tube that was failing showed very little sign of failure.

If you replace one of the outer tubes, replace the other outer tube. If you replace one of the inner tubes, replace the other inner tube.

Tubes are cheap compared to output transformers or circuit boards that can be fried by bad or failing power tubes.


3. Have your tech put a meter across all traces on the power tube circuit board. With the added heat from the tubes, the traces can eventually fail.


4. Have your tech re-solder all connections on the power tube circuit board.


5. Have your tech double check the Bias Supply after the amp has been played for 20 minutes or so, so that he can check it when the failure is occuring.


6. Have your tech clean and re-tension all power tube sockets.


7. A Mesa tech may be able to get a replacement board from Mesa, if they still have any. A really good tech could simply remove it and wire the power tubes in a Point to Point scenario. This would effectively remedy the problem for good, but might lower the amp's collectability.




If all else fails, PM me. I'm a Mesa Certified Tech that just happened to move to a place where the only Mesa amps in town are mine.


Let me know if this info helps.

 

[Boogie Bill]

Hey, thanks Monsta-tone!

I think my tech did all of that. Good to validate that he's a good tech.

Here' a bit of an update:

I was going to make the 200-mile trip this past weekend to take the amp back to him. But on Friday, I decided to get the amp out and let it rip for a few minutes. I ran it for about 25 minutes, with the OVERALL MASTER set to 4--about as loud as ever run it.

The amp still got got very HOT, and very quickly. Each tube (JJ-EL84s) appeared to be glowing about equally. The heat wouldn't be much of an issue, except is seems to be running much hotter than it used to. Midway through my test session, the chassis was uncomfortable to touch. It definitely runs hotter than my Class A Maverick 212 at comparable volume (using the Mav's tube rectifier).

The tone was thick, juicy and meaty--just like I would expect it to be. I did not experience any "chopped off" notes or "blattiness" like it did when I used it on the gig. Though, I should have run it about 45 minutes to have correctly simulated the gig conditions.

So, we decided not to take it back up to my tech, or at least not until I'm sure "I heard what I heard". This particular club is in an older building, with probably questionable wiring. I wonder if this could have been a "brown-out". I'll take the amp to some jam sessions this week and see what happens.

The other possibility is that perhaps I have a defective V-30 speaker, though is sounded fine during my test session Friday.

Any other thoughts would be appreciated.

Thanks,

 

[Monsta-Tone]

Hey Bill,

I don't think it's the speaker or it would do it all of the time. I haven't seen too many speakers that take 45 minutes to act up when blown. Usually it happens fairly quickly.


The DC-3's are notorious for getting very hot. I used mine at a 2 hr jam session and I couldn't touch the back of the chassis for 10 minutes. The handle bolts got very hot too.


A really good option that Mesa should have thought of is a Mark IV fan in a DC-3. You can bring a small oscillating fan to your sessions and place it so that it either blows into the amp (might add dust), or blows the hot air out of the amp. This should help a lot.


Also, you might see if the Power Tubes are matched to the spec that you need for the DC-3, which would be between a 4.5 and 6 on the Groove Tubes scale.

Bob at Eurotubes is one of the only guys that I know of who will do this for you (other than Mesa). He's a great guy to deal with and he straight up tell you what his tubes can & cannot do.

It could be that your tubes are causing the amp to run a bit hotter because the Bias is not set right.


Hope this helps.


I would be willing to bet that it's a heat issue related to the design of the amp and the circuit board for the Power Tubes getting a bit old, but it's hard to say for sure without being there.

 

[Monsta-Tone]

Another thing that you should consider, and I think I mentioned this earlier:

Replace the Bias circuit. I've seen Vintage Fenders do this and they worked fine for a while, but when they got good & warmed up, the Bias Resistor would drift off and the amp went all out of whack.


I would have your friend touch up all Power Tube board solder connections as well, and tighten the tube sockets.

You would be amazed at how many amps I've fixed just by tightening the Power Tube sockets and cleaning them.

 

[gp]

I own 2 DC-3's and the only tubes that I can use without the amp burning up are Mesa Tubes.

 

[plumptone]

Hey Bill. Monsta knows what he's talking about - he's helped me through a couple of dilemmas with my DC-3 as well. Like you, I tend to run mine with the master volume up around 3 or 4, which seems to give me plenty of headroom, and allows the overdrive to bloom. I've had mine for 8 years or so now, and I have worked the amp pretty hard in the last 3 or 4 years.

I've had a couple of problems over the years - but basically every time it has all boiled down to tube issues. (My last problem involved the eq circuit, which was not an inexpensive fix). The amp runs hot no matter what. I don't think there's any way around it. It's a compact little unit, and there's not much room for the heat to get out. Additionally, if you are driving it hard (or if it has been worked hard in the past) the tubes don't last very long - especially the power tubes. Every year now, as part of a preventive maintenance program I install a new set of matched power tubes, and so far that has prevented additional tube related problems.

In addition to making sure the tubes are good from the get-go (always a good starting point), I have found the following to be helpfull:

1. Always make sure the amp is not pushed back against the wall. You need air circulating back there. Also don't put anything on top (rack unit or anything similar).

2. Use a power conditioner. I have had problems in many of the rooms that we play with crappy power. Using a power conditioner helps regulate things, and at least takes one issue out of the loop (so to speak). The other great thing about power conditioners is that you can hook up all your externals to it and get a cleaner signal - no interference etc.

3. Check the footswitch cable - when it starts to go bad very strange things start to happen. I had a problem with mine, and thought it was a bad speaker. Not the case.

But basically, make sure your tubes are all in good shape and matched where matching is required. I've also use Bob at Eurotubes, and the stuff he sells is great - as is his advice about tube selection. He personally responds to e-mail inquiries - usualy the same day, which in itself is impressive.

Most importantly - don't give up on the amp. The DC-3 is truly a gem, and once it's running right, there's nothing else quite like it.

 

[Monsta-Tone]

Hey, thanks for the props.

These are great amps. I traded mine to a good friend who builds websites for a living. He needed a great amp, and I need a website.

I still have the DC-5 though. I want to sell my Heartbreaker and get another DC, maybe a 10 combo or another 3.[/code]