Crate KX-80 Keyboard Amp fuse pops immediately

[budm]

Re: Crate KX-80 Keyboard Amp fuse pops immediately

The Diodes are shorted.
The Zener 1N5353B 5Watts is 16V Zener Diode.
http://www.digikey.com/scripts/DkSea...google&cur=USD
So replace all 4 Diode, might as well order the Zener also, then power up and check the DC voltage across the Zener, it should be 16Vdc.

[ajsemtb]

Re: Crate KX-80 Keyboard Amp fuse pops immediately

should I go ahead and order the capictors also? the burned looking ones...

[budm]

Re: Crate KX-80 Keyboard Amp fuse pops immediately

Yes, get them all from Digikey, might as well get the Pansonic FM series 105c rating.
http://search.digikey.com/us/en/cat/...panasonic%20FM

[ajsemtb]

Re: Crate KX-80 Keyboard Amp fuse pops immediately

dont have fm series in what i need. HA and HB available...

[budm]

Re: Crate KX-80 Keyboard Amp fuse pops immediately

Since we are dealing with linear power supply, then you can use general purpose but must be 105c RATING

[ajsemtb]

Re: Crate KX-80 Keyboard Amp fuse pops immediately

OK, after all the searching, Digikey does not have the diodes I need in stock... is there another website? I usually use Digikey, so I don't know of another supplier..

[ajsemtb]

Re: Crate KX-80 Keyboard Amp fuse pops immediately

btw, the diodes are 1N5392 1.5A 100V

[ajsemtb]

Re: Crate KX-80 Keyboard Amp fuse pops immediately

i'm getting obsolete messages and not in stock messages at mouser, digikey, avnet, and a couple other sources from google... Any thoughts?

[mariushm]

Re: Crate KX-80 Keyboard Amp fuse pops immediately

Farnell (Newark) has them :

1n5392

http://www.newark.com/multicomp/1n53...00v/dp/01P4232
http://www.newark.com/nte-electronic...-5a/dp/33C7847

1N5353B

http://www.newark.com/multicomp/1n53...lar%20Products
http://www.newark.com/on-semiconduct...lar%20Products
http://www.newark.com/on-semiconduct...7aa/dp/10N9629

As for capacitors, I think you needed 100uF 35v - there's no 100uF 35v in the Panasonic FM series, there may be in the FR series but I'm too lazy to look it up now (later edit: nope, same with the FR, only 50v rated ones).

Anyway, you can go up in voltage rating with no problems, so then you have more choices.

Panasonic FR 100uF 50v will do:

http://www.newark.com/panasonic/eeuf...ial/dp/74R3440


This Rubycon ZLH 100uF 50v is relatively close in specs to Panasonic FM and Panasonic FR 100uF 50v, should have about the same specs as a hypothetical FM 100uF @ 35v :

http://www.newark.com/rubycon/50zlh1...ial/dp/39K2793

This 100uF 63v Nichicon PM should be acceptable... not as great as Panasonic FM or FR or the Rubycon above but i'd say good enough...

http://www.newark.com/nichicon/upm1j...ial/dp/65R3647



You may be able to use this Nichicon KZ 100uF 50v (Muse audio grade capacitors.. though doesn't matter where the capacitor is located):

http://www.newark.com/nichicon/ukz1h...ial/dp/70R1183

[budm]

Re: Crate KX-80 Keyboard Amp fuse pops immediately

You can go with higher Voltage and current rating for the Diode: 100v and 1.5A sounds kind of low to begin with.
http://www.digikey.com/product-detai...ICT-ND/1228202

http://www.digikey.com/product-detai...TPCT-ND/950500

[ajsemtb]

Re: Crate KX-80 Keyboard Amp fuse pops immediately

Thanks, order made. Now waiting on parts. Thanks for your help!!!

[ajsemtb]

Re: Crate KX-80 Keyboard Amp fuse pops immediately

ok, I got shipment #1 in. It had the caps and the zener diodes (what are zener diodes anyway, and what do they do?!) Installed those parts. The other 4 diodes had to be shipped directly from the manufacturer as they are not stocked parts anywhere, it seems. they should have been shipped out today so I'll have those in a couple days. Needless to say, i can't power on yet until those are in. Just wanted to give you all an update.

Oh, and I originally ordered the Nichicon 35v caps that matched, but also ordered the 50v Panasonics that were supposed to be better. I installed the 50v caps. I replaced all 4 (they were the yellow ones). Is there anyway to test the caps with a standard DMM that would tell me if they are bad? My DMM doesn't have the capacitance meter. I did however order the Peak Atlas ESR70 that should be here next week as well, so I'll be able to test all these caps that I've been saving from other projects to see which ones ACTUALLY failed, regardless of changing them ALL out.

[retiredcaps]

Re: Crate KX-80 Keyboard Amp fuse pops immediately

(what are zener diodes anyway, and what do they do?!)

http://en.wikipedia.org/wiki/Zener_diode

Is there anyway to test the caps with a standard DMM that would tell me if they are bad?

If the multimeter can't read capacitance, then there is no accurate way to measure uF. No multimeter can measure ESR.

[ajsemtb]

Re: Crate KX-80 Keyboard Amp fuse pops immediately

Just a short update, I got my Atlas ESR70 meter in. It confirmed the 2 "burned" looking caps were bad, as well as the 2 that weren't burned seemed awful high ESR. Glad I changed all 4. Still waiting on diodes.

[ajsemtb]

Re: Crate KX-80 Keyboard Amp fuse pops immediately

*UPDATE* Ok, got parts in. Installed the diodes for the bridge rectifier, decided to use my new Atlas ESR70 meter and on the in-circuit caps to test before I add power... Glad I did. (or better yet, wish I'd had it when I ordered the last set of parts... >;F I found a cap that indicated >40ohms, removed it from circuit and retested. Failed miserably. It was a 3.3uf 50V axial cap. While desoldering it and trying to pull it out, I grabbed the wrong cap, and pulled the leg out of the cap. Its a 1uf 50V cap... So great. Now I need MORE Parts that I know frys won't carry.

At Newark, the Multicomp caps are .06-.08. The NTE is .35. I was going to order extras, as I always do JIC. Any problems with the Multicomp caps, or stick to the NTE? No panasonics aren't available....

Tested all the rest of the caps in circuit, most of them are <10uf and had ESR readings from 3ohm-6ohms. All different amount. None tested bad though. The ones that I felt were kind of high, I removed, retested, tested good, so reinstalled...

[ajsemtb]

Re: Crate KX-80 Keyboard Amp fuse pops immediately

and the 3.3uf 50v axial cap is not available. could I use a radial leaded cap instead?

[ajsemtb]

Re: Crate KX-80 Keyboard Amp fuse pops immediately

OK, so I ordered the replacement caps, they will be here Friday. I ordered both the axial caps that are 3.3uF 63V (because the 50V were not available in axial) and I also ordered 3.3uF 50V "can" caps because they are the correct voltage. What I don't know, is which would be better? Anyone have an opinion? I know there shouldn't be anything wrong with going up in voltage, but can you use the radial caps in place of the axial caps?

[999999999]

Re: Crate KX-80 Keyboard Amp fuse pops immediately

The voltage on those is "probably" irrelevant (measure voltage while unit is powered on to be sure), when the uF value is so low it is just easier to make higher voltage parts that cover a wide array of circuits. Use what physically fits on the PCB better then what has better specs like temperature, ESR, etc.

If you were to reverse engineer the subcircuits and determine the role of the capacitors, then we might better determine if there's any realistic expectation that choosing a different capacitor type would be an improvement and then there could be a need to measure operating voltage since other capacitor types like film, ceramic, tantalum, have lower capacitance density per area and space available on the PCB would be more of an issue. For example in the signal path a film cap could be desirable or for decoupling, either film, ceramic, or tantalum. However since it is located in the speaker enclosure some ceramics may not be ideal as the vibrations can affect their performance.

[budm]

Re: Crate KX-80 Keyboard Amp fuse pops immediately

if the audio coupling was 3.3uF, you can use 4.7uf (most of the 1. 2.2. 3.3, 4.7uF will be rated at 50Vdc which are fine) it will give more extended low frequency response. In the high end audio if they use electrolytic for coupling, they will also use a small value cap (0.01uF polyester, non-inductive type, or ceramic) in parallel with the coupling cap. I do not have golden ears, some people do not want to use any coupling cap between audio stage at all.

[ajsemtb]

Re: Crate KX-80 Keyboard Amp fuse pops immediately

update, it works! Replaced 8 caps, 4 diodes, 2 zener diodes, and put it back together. Now, it is functioning as well as it did before it died, however, it still "pops" loudly when turned on, and off. Is there any reason for that? If its not a "oh that's a problem with the ...... and you just have to replace ....." then I'm not going to tear it back apart. If its a simple thing, I'll open her back up. Thanks again for all your help! Again, you have fixed yet another piece of equipment, and saved it from the trash!