Tapping a filter cap creates crackle

[pbman1953]

Happy Holidays!


The amp- Sunn/Fender 300T.


The amp has been distorting on an off for a while. No rhyme or reason. I could use it for a few hours with the band today and next week it may distort. I put the amp on a bench and started tapping everywhere. Once I hit the top of cap 171, (330uf /450v)there was an evident crackle. C 172 had no noise, 173 had a 1/3 as much noise as 171. I took the board out and re-soldered the points of all 3 filter caps. All 3 are radial 330uf /450 volt caps. 


Here's a link to the service manual-  https://el34world.com/charts/Schematics/Files/Sunn/Sunn_300t_service_manual.pdf


Could there be an internal issue with the caps?




Any suggestions would be appreciated

[shooter]

still crackle after re-solder?
typically crackle is bad connection, solder...
caps are goo sandwiched between metal so if the goo is drying, could cause crackle

[pbman1953]

Thanks, I guess I'll replace all 3 . 


Did a search and found these sites. I have no idea what brand I should get.




https://www.newark.com/c/passive-components/capacitors?capacitance=330uf&voltage-rating=450v


This one looks like the one in the amp now , based on color-


https://witonics.com/products/330uf-450v?variant=32347884421186&currency=USD&utm_medium=product_sync&utm_source=google&utm_content=sag_organic&utm_campaign=sag_organic&utm_campaign=gs-2018-11-19&utm_source=google&utm_medium=smart_campaign&gclid=CjwKCAiA25v_BRBNEiwAZb4-Zd1kL3RgUtb7_KiiKoVn2akD4W3cffyFwK8WCmFU_4NQ2h_YD9RfvhoCuVgQAvD_BwE




https://www.mouser.com/Passive-Components/Capacitors/Aluminum-Electrolytic-Capacitors/Aluminum-Electrolytic-Capacitors-Snap-In/_/N-75hr0?P=1z0wrktZ1yx4ard




I need  38mm h x 35mm dia- snap in straight terminals

[DummyLoad]

the mounting center is another important dimension? 10mm? 12mm? PCB plate thru hole size also important - measure the lead diameter if, it's square or rectangular measure across the long ends. the curved leads can be straightened with a pair of needle-nose pliers.

you need four dimensions:
body diameter
body height
lead center to center
lead diameter or width at the widest part if not round.

based on what you describe this part seems like it will fit: SLP331M450H5P3 - however, the part requires leads hole size of 2mm on 10mm center - that you need to confirm before ordering.

--pete

 

[pbman1953]

CAP AE RDL 330uF 450V 20% 105C


This is off the parts from the manual, does this help?

[pbman1953]

I took the number off the existing cap- BC 2222 159 57331.


I got this page-


For 330 uf/ 450 volt , it must be the 35 x 40mm


 https://www.vishay.com/docs/28341/159pulsi.pdf

[DummyLoad]

ok, so you have all the criteria:
105^c part
35mm dia
40mm length
10mm center2center
1.5-1.8mm lead size for 2mm PCB holes

these 3 parts are candidates. pick your brand poison. color is also important...   

--pete

[pbman1953]

Of the 3 brands, are there any favorites?

[shooter]

color is also important...   

caps should be caps, but I agree with Pete, color IS a consideration

[thetragichero]

they're all basically the same price. cde and nichicon are both "known" manufacturers (may be important for resale to snobbish types. cde possibly gets the leg up with these because it sounds more 'continental')
so yes, choose whichever fits your color scheme ;)

[DummyLoad]

i'd choose the part with the lowest ESR/highest ripple current rating. take those specs with a grain of salt. all 3 are 3000 hour parts. 


--pete

[pbman1953]

I went with the blue Cornell's. Lower ESR than the other Cornell. The Nichicon had no ESR rating


Thanks for the help!


BTW- Mouser is offering a holiday special of UPS second day at the same price as ground. They're smart because they know bad  USPS us performing lately.

[trobbins]

Just to clarify please - did it continue to crackle when tapped after the soldering action, or didn't it go back in to the amp?

[pbman1953]

After soldering, no change, still crackled

[Latole]

Thanks, I guess I'll replace all 3 . 

Amps is not old enough to need to replace caps.

By hitting the capes, the vibration can act elsewhere on the circuit

Post picture.

https://www.facebook.com/c4soundworks/photos/pcb.635952676969073/635951490302525

[Latole]

After soldering, no change, still crackled

Did you dismantle all printed circuits board to have access to the solders under  ?     

[pbman1953]

I tapped everywhere and sometimes without mercy but with in reason. Plus I including all the resistors around the caps. In the end, tapping the top of C171 still prevailed. After I re-soldered C173, it's crackled seemed to go away. 


Yes, I removed the board, flipped it over and re-soldered all 6 contacts for all 3 330uf caps

[pbman1953]

One thing I noticed about the spring-loaded pre-amp tubes covers. Before I started unscrewing the board I took out the pre-amp tubes. When in place they push and pressure the board. That's when I noticed the board's relief after they were off. I put the pre-amp tubes back in for testing without the covers. I may leave them off because this amp rarely leaves the house.




The spring loads for the power tubes will stay on. They cause no harm

[pbman1953]

I decided to remove the caps to see if there were traces under the caps. Low and behold 2 caps were hard to take out because there were traces under the caps making that you need 2 tacks to make the connection. I'm a novice-to intermediate compared to many of you but it's beyond me how anyone could design large trace connections under a part that covers itself. Looks like you're banking on the heat and the solder flowing though to make the connection. Plus hopefully the solder reaches the terminal base rest on the trace.  I'm sure there are some real savoy solder technicians out there , but a connection under? Sadly 2 traces lifted so I'm going point to point on the bottom side.


I'm sure that the real problem was the connection under the caps. But, the caps are still going , they're all dented and I have no idea why.


Plus for all you Mouser customers, they are offering UPS 2nd day for the same price as USPS. I think I saw the same if you want
FedEx too

[sluckey]

Double-sided PCBs have thru-hole plating (kinda like a tiny eyelet). You apply solder to the bottom side of the board only.

[pbman1953]

I guess that's ok for space saving or design, I'm not fan. Seems ok for the first install and a hassle for a tech. Unless you have a technique.

[sluckey]

That's just the way it is with complex pcbs. IMO, a vacuum operated desoldering station is a must for this type repair. Not many amp hobbyist have such a tool. And they botch the pcb trying to use their soldering iron to do a desoldering job.

A soldering iron and solder braid can do a nice job on a single sided pcb. Sadly, most people in these forums don't even have solder braid.

[pbman1953]

Vacuum sounds very cool. I could see that as an must for a daily tech. I do use braid but my best buddy is my solder sucker, a Soldapullt. It has so much power many times I don't need to use the braid to clean up. 

[Latole]

That's just the way it is with complex pcbs. IMO, a vacuum operated desoldering station is a must for this type repair. Not many amp hobbyist have such a tool. And they botch the pcb trying to use their soldering iron to do a desoldering job.

A soldering iron and solder braid can do a nice job on a single sided pcb. Sadly, most people in these forums don't even have solder braid.

I agree.

[sluckey]

The Soldapullt is a fine desoldering tool that should be in everyone's toolbox. I use mine for almost all of my tube amp work.



But when I do pcb work (very little these days) I always fire up my PACE work station. The variable temp iron with hollow tips and footswitch operated vacuum pump make an easy job of removing small multi legged critters such as DIP ICs or even a 2N2222 from single sided or dual sided boards. With a little experience it's hard to tell that a component has even been replaced. It's hard for a hobbyist to justify the cost of the PACE or similar workstation though.

[pbman1953]

Here's a new item I bought months back. It's 30w with good suction. Nice bench!

[centervolume]

Sounds like you have it under control but for future reference (Don’t know if people still do this) but I’ve found that unless it’s with pots, crackle involves cracked or arcing resistors a significant part of the time, especially ones in higher voltage roles like what you are dealing with. Doing the chopstick test in a dimly lit area will often reveal arcs quickly because they spark up.

[pbman1953]

Once I get everything back together, and if the issue stays, I can try your dim light test.
Thanks

[pbman1953]

Caps are installed with no more noises. Either it was the cap or the under cap solder points having a bad connection. But since the last set was all dented up I'm happy to have fresh set in there.


Is there a need to re-bias?


Thanks for the help!!

[sluckey]

Is there a need to re-bias?

I would.

[dude]

Very easy to destroy a trace on a PCB, too much heat is the main reason. The trace will lift; then you have to use wire to recreate new traces. The solder sucker, braid and flux will make the job a lot easier. Flux the trace add braid and heat, solder will flow into the braid should leave the trace shinny, tinned and free of all solder.

[pbman1953]

I'm back for a little more help. No worries all's great! The back story is that I used to have a first 300t back in 2000 but I had to sell to consolidate gear for a move from a work play space to home. The first 300t was scary and amazing. This 2nd one had the power but never had the scary aspect to it. Now it does.  I remember on the first one I could push the master to a high level and simply use the Gain #1 as a volume control. There's a lot of controls on this beast but I treated it live a SVT or 2000s, simple.  For the second one I couldn't do that, it would get noisy. But now it can.


So I'm wondering since there were 5 connections, under the caps surface, were bad what's the difference with them all connected now? What did the connections do to make it work right again?


The cap's replaced were 171,172 and 173. They were also trace connections under the cap, component side to , I think R323 R316 and diode next to r314, that I can't read. Meaning that some parts were soldered on both sides.


But Here's the link to see the manual-


https://el34world.com/charts/Schematics/Files/Sunn/Sunn_300t_service_manual.pdf




I'm wondering if anyone can figure out what made the difference of the 5 contacts that weren't connected before. It's for personal knowledge because this amp from the get never had a chance because I bought it with this issue. Now it's back to being amazing and scary and quiet

[glass54]

Hi pbman1953
Regarding the Soldapult device, I used one for many years and it is very important to regularly clean the insides. Failing to keep the unit clean, means you may have to have a second or third attempt to desolder. Not good for the board. If your joints are a little oxidized, I suggest a drop of RMA flux (or equivalent) to help solder "gather" when heated making the job easier for Soldapult.
I was in very fortunate position to buy my own Pace Desoldering station a couple decades ago, so I rarely use a Solderpult these days.
But same goes for tips and glass barrel in Pace station ie MUST keep Desoldering Tips and tubes very clean or clogging occurs and you have issues.
Kind regards
Mirek

[pbman1953]

Thanks for the heads up, but I'm right with you. I clean it regularly.