Need DB Technologies SUB 05 or SUB 12 subwoofer amplifier schematic

[mariuss77]

I wouldn't gamble with a burnt one even if it is usable with an external R.
In my case all the transistors in final stage are gone as the ex owner took them down and lost them.
But with your help now i managed to find out what they are and i will purchase them soon and hopefully repair my sub.
Also if someone here does have the schematic for the Blue Sky 2.1 mk1 studio speakers sistem or for RCF Art 422 mk1 it will be very helpfull because i also have these ones laying around for service and i can't find any schematics for them.
Many thanks!

[izzzzzz6]

The Sanken SAP16 transistor had an emitter resistor on it's output pin, built in to the transistor.

The replacement, STD03, does not have this feature.
So one must add the emitter resistor to the existing circuit.

The emitter resistor (or more commonly, the 'ballast' resistor) generally goes to the speaker out.

Guys i have learnt quite a bit from you in this short discussion. I went to my lockup today to check out the amplifier (which has been sitting there for a few years now and it's not actually a SUB 05 but it is a SUB 15, it still uses SAP16's i think 4 of them and to either side are 2x IRFR140N I'm guessing these are the drive transistors. Second from the end of the row is an LM337 and the last one is difficult to read but seems to be something like (LM332T then under that it seems to say GK05K VU then under that i think it says CHN 536) I guess this is another pre drive transistor. Sorry i'm not taking the time to search all of these components.
If the protection light is coming on then is it worth checking all of these transistors or should i first look elsewhere on the circuit?
Sorry i need to do some catching up with my electronics knowledge. I do generally manage to fix quite a lot of gear, but i've quite a backlog at the moment, including a Lab Gruppen fp6400 which suffered a problem with the switch mode supply when the main transformer became unglued sending a spike through some of the circuit blowing capacitors with a show of loud bangs and sparks flying and finally tripping a 32 or was it a 64A breaker at the far end of a long building! I'm hoping to glue and clamp the transformer back together, replace the capacitors and go from there on that one.
James

[izzzzzz6]

@Jazz , thanks for clarifications, i did some research about and i find out that the resistor blows before the junction and thus being responsible for the part replacement with STD's.
After this i am aware and more biased to work with STD's instead of SAP's even if that needs the external resistor.

@ The Dude, thanks for feedback and link, Tuesday i will search in local market for STD's/SAP's and in my pile of late 90's home amplifiers, some of them very powerful discrete amps. The SAP16 look very familiar to me and i might saw them in one or two of these amps, maybe i get lucky.

Cheers!

Hi Mariuss
Sounds like you know a little more than i do here but i just thought i would mention that you should try to get the SAP16 NY and SAP16 PY in the correct order on the board, i don't know how similar the sub 05 board is but on my sub 15 the NY's are on the left side and the PY's are on the right side as you look at them. You had better check that.

[doctor]

Guys i have learnt quite a bit from you in this short discussion. I went to my lockup today to check out the amplifier (which has been sitting there for a few years now and it's not actually a SUB 05 but it is a SUB 15, it still uses SAP16's i think 4 of them and to either side are 2x IRFR140N I'm guessing these are the drive transistors. Second from the end of the row is an LM337 and the last one is difficult to read but seems to be something like (LM332T then under that it seems to say GK05K VU then under that i think it says CHN 536) I guess this is another pre drive transistor. Sorry i'm not taking the time to search all of these components.
If the protection light is coming on then is it worth checking all of these transistors or should i first look elsewhere on the circuit?
Sorry i need to do some catching up with my electronics knowledge. I do generally manage to fix quite a lot of gear, but i've quite a backlog at the moment, including a Lab Gruppen fp6400 which suffered a problem with the switch mode supply when the main transformer became unglued sending a spike through some of the circuit blowing capacitors with a show of loud bangs and sparks flying and finally tripping a 32 or was it a 64A breaker at the far end of a long building! I'm hoping to glue and clamp the transformer back together, replace the capacitors and go from there on that one.
James

The SUB05 and SUB12 schematics are the same.

[mariuss77]

Hi James,
great picture, i think same applyes to my sub but in half, eg. 2 SAP's and 2 IRFR's instead of 4 as you have.

Regarding your troubleshoot, i'll start with easy things first and build my way up if it is the case, i am sure you did it but here is what i'll do:
First, check the speaker with a multimeter if it is ok, i assume 8ohm...
Since is a powerful subwoofer you might have loose connections or soldering due to vibrations so a recheck of continuity in wires and resoldering of all components in pcb may be a place to start.
Then , do a very good check of the capacitors, ideally with an ESR meter or good capacimeter, sometimes bad caps aren't inflated so you can see with naked eye.
Also resistors may become damaged due to excessive heat or vibrations.
I am pretty sure you did all this checks already but worth a mention..
Cheers!

[mariuss77]

@Doctor
Thank you for schematic, that s gold, the cherry from the cake in this thread, i am very glad i asked for your help guys!
Very helpful community here, i own you a beer to all contributors in this thread

[mariuss77]

Ok, i did ordered the original parts consisting in SAP16p/n and IRFP's 140/9140 and in a few day they will arrive.
I had some pictures taken for you to see the level of damage done by the "pro" repair technician that previously "worked" on the amp.
Now, i cleaned the board and resoldered all components with good flux, tested components and repaired sectioned tracks, everything seems to look ok.
I will keep you updated.
But i have a question regarding two jumpers like connectors that i assume that are for testing purposes but maybe they were connected or something?
Maybe you can shed some light over them because the schematic didn't.
I attach the picture here, thanks!
link to pictures: https://www.flickr.com/photos/123801753@N06/

[paleeman]

Yup, you're right. Those are just test points.

Cheers

[mariuss77]

Great to hear that, thanks for clarifications Paleeman!

[mariuss77]

Ok, so i did receive all original transistors and replaced them, but the result is very dissapointing.
Now the leds won't come on but the fan blows air and the speaker has a loud hum at around 150Hz, no musical signal is heard and no delay or pop on on/off.
It seems that temperatures are ok around pcb or on components, nothing is getting overheated.
It's weird that no led is lighted and i suspect the NE5517 to be the blame.
or...the IDLE CURRENT jumper is in fact connected with TP TEMP jumper. I think i have a very big DC offset because of that but not sure.
Any suggestions are welcome!

[izzzzzz6]

Hi Mariuss
I am about to have a closer look at my sub 15. I don't know what to suggest regarding your problem but in the schematics does it give you any reference voltages to test for? Perhaps try to check to see if the power supply is working fully, is there a voltage regulator you can check?
Then if the PSU is ok... Can you follow a signal through the board? Do you have a scope of some sort? If you can get a scope perhaps you can see what happens to the input signal, and where the noise is coming from. There may be an issue with the preamp. Keep us posted with your progress, i'm about to check my SAP 16's and all the main resistors. My amp go's into protect mode after a few seconds so i'm hoping to find out why in the next few hrs. I'll keep u posted.
James

[izzzzzz6]

My findings and thoughts out loud

I was about to report my findings as i looked at the amp but it was a few hrs after the domain name had expired (as some of you may had noticed, the site was down for a few days). I pasted my notes into stickies so here they are now (i currently am waiting for the parts to arrive). :

Here is what i have discovered whilst problem shooting my SUB 15 amp.
There are 4x 10ohm 5W resistors that appear to be blown, they are almost short circuit and showing almost no resistance. They go in series between the Source pins of the two IRFP9140N's and also they are in parallel from those two pins to the centre Collector pins of the PY SAP16's, it's the same between the Source pins of the IRFP140N's and the NY SAP16's
(I correct myself the resistors are .10ohms not 10ohms so they are ok i wasn't testing low enough on my multimeter).
Also one of the IRFP140N's appears to be blown.

The voltage regulator LM337 Which is mounted along the row of power transistors appears to be blown but i'm not sure if i'm testing it properly, If anyone could tell me how to test one of these i would appreciate it. (i guess i need to put a voltage into it and see if it works, unless there is an easier way?)

I'm not sure if i'm testing the SAP 16's correctly, they appear to be ok but how do i test to see if the internal resistors are blown or not? It appears that you should be able to test for resistance between the Base and Emitter of the SAP16's but i am getting 750 ohms, i'm not sure what the resistance of the two diodes in series should add up to but i'm guessing around 1100 ohms but then one of the internal diodes is in parallel with the two internal resistors which i would imagine add to just under 100ohms as there is a 100 ohm in parallel with the .22 ohm resistor so in that case if one diode has a resistance of 550 ohms and is in parallel with approx 99ohms = 83ohms + the resistance of the other diode in series = 550 + 83 = 633 ohms, since i have no idea what the resistance of the diodes inside the SAP 16's should be i am only throwing out some rough estimates, it doesn't seem too far off of the 750 ohms i'm getting but there is no way to test the .22…….. oops i've just noticed that the .22 ohm resistor is between the Source and the Emitter of the 16N and the 16P they test ok so all seems to be ok with the SAP 16's.

I'm going to order a new IRFP140N and a LM337 to compare and perhaps replace. If anybody can think of any other parts or points i should test here please let me know.

Mariuss, i noticed that when trying to remove the SAP16's that many of the connecting points between the double sided board were damaged and some came out altogether (i need to get a decent motorised solder sucker with heated tip) so this may also be the case as from when your previous amps owner removed them, i would suggest checking continuity between the legs and the relevant parts of the circuit as the solder may not be connecting to the other side of the board any more. Also check continuity where there are some smaller tracks on the board as the removal of the SAP16's may have damaged where these tracks join to the solder points. After checking through a cambridge audio A300 hifi amp today that had a blown SAP10 i noticed that it had caused too much current to flow through quite a few other components and fried a few of the smaller bits and pieces around that PNP transistor's immediate circuit, although saying that the A300 does't have any protection like the Sub15 does and i imagine thats the same protection circuit you have. Did you get any further with the amp yet?
James

[mariuss77]

Hi James!
Thank you for reply, i also taught that the forum was down forever and so upset until i found your reply email
So, sorry for the late reply...
I did check the voltages and everything seems to be ok, i think the problem lies in the active crossover. Unfortunately i do not own an oscilloscope to trace the signals.
I was also triple checked the trays on pcb compared to schematic and everything is fine.
From what you say and measured i think your SAP's are fine.
For now i am awaiting for the NE5517 to arrive and i will keep you posted.
How yours does now? Did you managed to troubleshoot further?
Just a guess but i think the problem in yours lies on the voltage regulators LM317/337, do you get the +- 15v on pcb?
Cheers!

[izzzzzz6]

I am waiting for the parts now. They should be here this week or next week. I think i will have to apply a voltage to test the voltage regulators. I have been worried to apply an input voltage to the board with so many parts taken out of circuit, i'm sure it would be fine but i didn't want to take the risk, i think that your correct and that one of the regulators blew when the pre drive transistor blew. It's hopefully only those two parts. It's a shame you don't have an oscilloscope, neither do i. I had a very nice one many years ago but i left it with a friend and i don't know how but he lost it! I was thinking to replace it with one of these:
New Mini AVR DSO150 Digital Storage mini pocket Oscilloscope With USB Cable agz | eBay

Or even better:

ARM DSO201 Portable Pocket-sized Nano Handheld Digital Storage Oscilloscope ahn | eBay

Fairly affordable.

I saw a video on youtube of a guy who repairs and replaces an preamplifier chip on a Mackie srm 450. It's possible your amp uses the same pre amp chip so it could be worth watching?

https://www.youtube.com/watch?v=oHCC2524Bk4

Good luck. let me know how you get on.

[izzzzzz6]

The amp is now repaired, i replaced one of the voltage regulators LM317 or LM337 can't remember which but the other was ok, also i was going to replace only one of the IRFP140N's but the new IRFP140N's and the new IRFP9140N's seemed to have slightly different values to the old ones, i think i ordered slightly the wrong parts as there was another number on the fets that didn't match up, so i replaced all 4 of the 2x IRFP140N's and the 2x IRFP9140N's with the new ones so they would match better. Amp works fine now and will test it fully tonight at a small party that i am dj'ing at.
Marrius did you have any luck with your amp repair?
Ps. Does anyone know how or if it's possible to match an amp to change the load connected to it, i.e.. if i wanted a 4ohm speaker connected or if i wanted a 16ohm speaker connected is there a way to set this up by changing something in the amp's output stage?
Happy this is working again, got a few more repairs to do over the next few months!
James