Massdrop Cavalli Tube Hybrid Amp

My socket savers aren't flush on my MJ2 either; I just use something like a popsicle stick (technically it's my wife's nail file) to hold the saver down while I wiggle the tube out. You only have to do this a couple times before the socket on the saver itself loosens up a little to not require this trick anymore.

 

Well, I just discovered that it's definitely NOT a good idea to stack 2 socket savers when one of them has a short between pins 3 and 4. During the power up sequence while the LED was still red, there was a big pop and a large puff of white smoke. At first I thought maybe the LPS had gone over voltage, but it's still outputing 28VDC. After the smoke cleared, it was pretty clear that a cap beside the socket (beside R107) had exploded.



I then took apart the savers and the first one looked fine. The 2nd one however had some really manky soldering. I didn't realize the pins were soldered in place.



Is there any chance that just replacing the blown cap will revive the amp?

Damn, I'm really bummed. I just got the LPS home yesterday ...


Edit: Popped the back cover off and found (one of) the culprit(s).

 

^^ Ouch. Sorry to see this happen. Most all of us have been there before. It's a sick feeling.

 

^^damn

 

@gixxerwimp

Wow, that's really bad. We should all probably check our socket savers and adaptors for bad workmanship before using them! I have a black 5670 to ECC88 adaptor similar construction to your saver (which I use with Vali 2), I will check it although it has never caused a problem. I wonder if the silver ones are better made?

Looks like your avatar is apt (again). But this time not your fault. Really bad luck. You should obviously complain to the socket saver vendor, but it seems unlikely they will be amenable. Maybe Massdrop can be of some help?

 

I hate to say it, if I were Massdrop I wouldn't do much here. Socket savers and out of spec tubes aren't a warranty issue. Can't blame them if that's what they say.

It's really unfortunate.

I'd be all over the maker of that socket saver though. As in, full refund, replacement of the amp, etc.

 

Pin 4 carries the current for the tube heater circuit so I guess that's why you had the fireworks. Maybe the cap blowing saved your board, maybe not. Seeing as you are way way outside this being a warranty issue I would try to fix it at home.

I have some socket savers but after seeing what was inside one of them I never used them. It's just a bunch of waste metal in your signal path.

 

You wouldn't happen to have a link to the socket saver you have would you? I'm seriously considering one...thanks!

edit: I just read about the socket saver/blown amp. That REALLY sucks...I agree with Elnrik, I'd be asking for compensation. Good luck man.

 

http://www.tubemonger.com/NOVIB_Socket_Saver_1960s_NOS_British_McMurdo_B9A_p/novib-mcmurdo.htm

I know this costs more than ebay, but I felt way more confident in what I was getting from these guys.

 

Yep those are high quality pieces.

 

Thanks for all the "condolences"! I guess I took being a guinea pig too far with the cheap socket saver I was able to source locally.

Now I'm wishing I'd spent whatever it would cost to have one of these sent across the Pacific. It also seems exactly the right height to be flush with the top of the chassis.

Posted "feedback" to the online seller I bought it from (Taiwanese equiv. of eBay). I'd say pretty much zero chance of any compensation for the amp. Maybe he'll refund me what I paid him, which was less than the cost of Big Mac and fries.

I pinged dB and he said more or less the same thing, and gave me some voltages to check after replacing the cap. I knew I was pretty much out of warranty when I made it public knowledge I was using the AliExpress LPS

I just popped the board out of the chassis, after I finally figured out that it comes out together with the front panel out the front, and not the back (simple, ingenius design by the way). Cleaned up all the the cotton shrapnel and nothing else seems to have been damaged. Will source a replacement part and try to get her back up and running.

 

It is - I'm considering pulling mine and painting the top black... I'm annoyed by the white ring on the black chassis (I know... minor problems)

Good luck on the repair... really sucks

 

I got a replacement cap and will swap it in shortly. I forgot to ask dB if I should measure the voltages with or without the tube installed.

Also, is the tube that was installed when it blew now suspect? It looks fine (no signs of cracking as previously described described by @dBel84, and all the wires inside look OK), but should I not use it?

 

New 100μF 16V cap in place.

I couldn't identify a "ground" to measure pins 1 and 2 (negative terminal of input power didn't work), but did measure 6.3VDC across pins 4 and 5. So powered down, plugged in the tube and powered up again ...

No fireworks. w00t!


Connected up the inputs, and ... muzak!

Back to the little MDF cave where it usually lives and hooked it up to the LPS and Eitr/Modi Multibit. Sounds pretty much like it did before I blew it up. Placing an order for the tubemonger socket saver right now.

When the wife came out to investigate the ruckus last night, she noticed the addition of the LPS in the corner and raised her own ruckus. I tidied it up as best as I could, stacking the Cthulhu on top to minimize the footprint.



We now return you to your regularly scheduled programming.


PS: I think the power-sequence takes 20 sec with the stock SMPS, but is consistently taking around 25 sec with the LPS. Not sure what this indicates or if it's of any significance or interest.

 

Sorry for hogging this thread lately. But I just saw this socket save on the tubemonger site:
http://www.tubemonger.com/NOVIB_CS_Socket_Saver_Vibration_Red_B9A_NOVAL_p/novib-cs.htm

I guess the centre screw is to secure it to the onboard socket, making it unnecessary to hold the saver down while removing tubes.


I didn't pay close attention when I had the board out, but I don't think there was a hole in the PCB. So I guess one would have to drill a hole in order to use it. Assuming it was done properly, would it be advisable to "try this at home"? Is there a chance there are any traces in the PCB running under the centre of the socket?

 

Drilling an already populated PCB sounds like asking for trouble*. In the very best case you spray bits of dust (some conductive) all through the components. If you really want a firmly connected saver, perhaps a high temperature adhesive would work.

Personally I like the tube being half hidden and won't tube roll so I'm not making temporary or permanent changes to the amp.

*I've never tried anything like this, this is based purely on the times I've broken through boards by hand when I'm too lazy to degauss hard drives.

 

@gixxerwimp the pins on the socket saver will loosen up after a few insertion cycles (I have the Tubemonger savers). So if you plan on rolling often you could always try to loosen it by inserting and removing your old socket saver or dead tube or whatever into the new saver while it's outside of the amp.

 

The traces do not run exactly in the middle but they are close - there are 2 as well as some resistors under the board.

I would recommend against screwing it down but you could always use glue to lock it into the socket below.

..dB

 

Thanks @JustAnotherRando and @famish99 (edit: and @dBel84) for saving me from myself. I occasionally get a little carried away and grab onto something like a bulldog. You guys must think I'm now intentionally trying to kill it

I'll go for the standard saver w/o centre screw.

 

I was literally typing "Bro - Just borrow my .44 mag and put the damn thing out of it's misery."