KLA10 Guitar amp with TDA2030 chip

[Micorina]

This post describes a burning.... My son's Violin/Guitar KLA amplifier started smoking and a loud hum.m.m came from the speaker. Couldn't have happened at a worse time for him with a Group Class Concert on Saturday 26th March. I have dismantled the unit and, apart from the TDA2030 getting immensely and hugely HOT I can see no other identifiable reason. Does anyone have any ideas as to why the circuitry should produce this horrid phenomenon? If it's the TDA2030 which has copped it, where can one buy a replacement? Michael

[firechief]

DigiKey has got them.
Linear - Amplifiers - Audio | Digi-Key
It might not have gone By By. If you have an ohmeter you need to check for shorted componets. Possibilties include the power supply capacitors, and the power supply diodes. Here is where a schematic would be helpfull. The power supply caps are probally the biggest caps in the amp. There should not be 0ohms accross them. Do you intend to troubleshoot it yourself? If so, folks on the forum will probally walk you through it. How much time do you have? Oh -- and post the brand and model number of the amp.

[Micorina]

Thanks Firechief! I do propose troubleshooting myself. Having successfully fixed my Gale Storm 8 Subwoofer problem (capacitors) I'm all set to get in there! Thanks for the tip. I'll try the power smoothing caps first for '0'ohms or whatever. The Amp (with 8" speaker in the box) made in China for Kustom Music, Cincinnati, Ohio has no other identification other than it is a KLA10. with a power input 40Watts Maximum 230VAC 50Hz. and a Power Output of 12 Watts Maximum 7v rms 4 Ohms. Unhelpfully the two Power smoothing caps are stuck together with hot glue and their values are unreadable. Prising them apart I find: 25v 1000uf +85deg. CD-SG (whatever that means!) Measuring across each cap in the power cct I get 160 Ohms reading on my cheapo RX10 scale. So they're not 0 Ohms. Hmm. Yes, I agree, a Cct Diag would be v.useful! Michael

[Micorina]

The Diodes I'm measuring now: Across their soldered contacts. Two pairs of Diodes each pair having a common connection (thus satisfying the full-wave rectifier Cct?) In the first pair of Diodes we get 200 Ohms in one direction and 160 Ohms in the other. In the second pair we get 200 Ohms in both directions. I have a smeaking feeling that those 1000uf caps were discharging on my first reading - which was 160 Ohms and quickly raised to 200 Ohms. Strange thing is there's a fuse on this PCB which hasn't blown... No other I.D. except each component is helpfully marked on the PCB by such writings as D5 D6 D7 D8 D9 D10 (those last four being the rectifier Cct) The resisitors are all marked as expected R1, R2.... &c. There's even wire straps in there mareked as W1 W2 W3 W4. There's also my friend from the Subwoofer in there too - a chip called 45580JRC. There's that other pair of smaller Diodes close by the TDA2030. One reads 40 Ohms in both directions, but the other... reads 0 Ohms in both directions. Do we have our rogue component do you think?? Michael

[Micorina]

I have removed one of the suspect diodes and measured it with my Ohm meter. Whereas in the Cct it reads 0 Ohms, out of the Cct it reads 200 Ohms in one direction and ~ Ohms in the other. So I unsoldered one end of the other Diode and measured it which produced identical readings. ergo those Diodes are OK. Now this is where a Cct Diag would really come in useful. Being in close physical proximity to the Integ. Chip TDA2030 I am wondering whether the chip itself is suspect. Michael

[Micorina]

You asked how much time do I have...? Well, if I can fix it on Friday (tomorrow) that would be wonderful as my son's Group Electric Violin Concert is on Saturday morning. Somehow I doubt I shall manage this so my son has cobbled together an amp using the speaker unit and a separate amplifier. However this cannot continue indefinitely so I must fix his KLA10 pretty pronto. Michael Sussex, UK

[firechief]

OK - good troubleshooting so far, sounds like its time to buy the TDA 3020
In the UK check out Farnell at this link.


Browse for Products | Farnell United Kingdom

They are cheep so I suggest that you get one on the way. Unfortunetally the shipping will cost more than the part so Im trying to think of anything else you should get at the same time.
I think you are right about the diodes, when they go they usually read 0ohms in both directions.
I expect more people to chime in anytime.
Bob

[Micorina]

Many thanks for this UK link. I accessed DigiKey in the US and was horrified at the postal costs - min $35 to UK so I'll try Farnell. Out of the Cct board the two Diodes test OK. Early am UK Michael

[Micorina]

Found minimum order from Farnell = £20 (about $40) Cheaper to replace amplifier...
Michael

[Micorina]

OK - so 'Thinks - what about ebay??' Found a TDA2030 for sale UK inc p&p £4 approx. There are several on that site - even including made-up amps on PCBs. Wonderful!
Michael