Speakerplans.com Homepage
Forum Home Forum Home > General > Amp Forum
  New Posts New Posts RSS Feed - Bad output device?
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Bad output device?

 Post Reply Post Reply Page  <1234 5>
Author
Message
AJordan View Drop Down
Young Croc
Young Croc


Joined: 06 July 2007
Status: Offline
Points: 1013
Post Options Post Options   Thanks (0) Thanks(0)   Quote AJordan Quote  Post ReplyReply Direct Link To This Post Posted: 05 April 2018 at 6:04pm
OK, so I did all that and powered it up. Got about five seconds of loud hum then it started to crackle so I turned it off. The fuses are still intact.

That cable must have been loose for quite a while, it didn't reach to the HF driver terminal. I had to take out the LF and rotate it to make the cable reach.

Anyway here are some pics.
https://www.dropbox.com/s/5h1mdeo2xcxddyn/IMG_6017.JPG?dl=0
https://www.dropbox.com/s/fwndzw6xe9yxyv8/IMG_6018.JPG?dl=0
https://www.dropbox.com/s/cauk27wmm48hsek/IMG_6023.JPG?dl=0


Back to Top
Hemisphere View Drop Down
Old Croc
Old Croc


Joined: 21 April 2008
Status: Offline
Points: 2272
Post Options Post Options   Thanks (0) Thanks(0)   Quote Hemisphere Quote  Post ReplyReply Direct Link To This Post Posted: 05 April 2018 at 6:14pm
Guitar monitor has tweeter unplugged, musician doesn't notice shock! LOL
Phase 1: Post on Speakerplans
Phase 2: ?????
Phase 3: Profit!
Back to Top
jbl_man View Drop Down
Moderator Group
Moderator Group
Avatar

Joined: 12 January 2005
Location: London.
Status: Offline
Points: 11154
Post Options Post Options   Thanks (0) Thanks(0)   Quote jbl_man Quote  Post ReplyReply Direct Link To This Post Posted: 05 April 2018 at 6:16pm
Disconnect the speaker, put your voltmeter accross the output terminals,DC setting,what does it read?
Be seeing you.
Back to Top
AJordan View Drop Down
Young Croc
Young Croc


Joined: 06 July 2007
Status: Offline
Points: 1013
Post Options Post Options   Thanks (0) Thanks(0)   Quote AJordan Quote  Post ReplyReply Direct Link To This Post Posted: 05 April 2018 at 7:52pm
Originally posted by Hemisphere Hemisphere wrote:

Guitar monitor has tweeter unplugged, musician doesn't notice shock! LOL


LOL to be fair it was a bass.
Back to Top
AJordan View Drop Down
Young Croc
Young Croc


Joined: 06 July 2007
Status: Offline
Points: 1013
Post Options Post Options   Thanks (0) Thanks(0)   Quote AJordan Quote  Post ReplyReply Direct Link To This Post Posted: 05 April 2018 at 7:52pm
Originally posted by jbl_man jbl_man wrote:

Disconnect the speaker, put your voltmeter accross the output terminals,DC setting,what does it read?


27.2 and still not blowing the fuses.
Back to Top
Muckerbarnes1 View Drop Down
Old Croc
Old Croc
Avatar

Joined: 20 March 2010
Location: Stroud
Status: Offline
Points: 2654
Post Options Post Options   Thanks (0) Thanks(0)   Quote Muckerbarnes1 Quote  Post ReplyReply Direct Link To This Post Posted: 05 April 2018 at 9:55pm
If you have 27V on LS o/p don't put speaker back in circuit. The crackling and hum you describe and assuming your check of o/p devices is correct, suggests to me the bridge rec is duff. As previous, take it out and test it. 

Check as before with your DVM, also check it in high resistance setting for reverse reading, often a diode can read ok on those gadgets, but show it's fault with a resistance in reverse, where there should be none at all. 

If there is a cracking from the PCB, something will be getting hot. I would of thought you'd have found this easily. 

Oh, and pictures...
Billy Dawg.
Back to Top
AJordan View Drop Down
Young Croc
Young Croc


Joined: 06 July 2007
Status: Offline
Points: 1013
Post Options Post Options   Thanks (0) Thanks(0)   Quote AJordan Quote  Post ReplyReply Direct Link To This Post Posted: 05 April 2018 at 10:31pm
Cheers Muckerbarnes1! No I won't reconnect speaker, I know DC aint good for voice coils. Crackling sound was from speaker. Funilly enough, the bridge rec was one of the first things I tested because it looked as though the heatsink paste had been melting. But, I tested it in circuit and as I am learning from testing the transistors that is not always an accurate test. Will pull it out tomorrow and try the tests you suggested. Cheers!

Oh, and pics should be a few posts back up.


Edited by AJordan - 05 April 2018 at 10:32pm
Back to Top
AJordan View Drop Down
Young Croc
Young Croc


Joined: 06 July 2007
Status: Offline
Points: 1013
Post Options Post Options   Thanks (0) Thanks(0)   Quote AJordan Quote  Post ReplyReply Direct Link To This Post Posted: 06 April 2018 at 4:38pm
Rectifier is out and tested. In diode test I'm getting between 700 and 720. Testing resistance I am on the 2000K scale and getting between 1300 and 1950 forewards. and open circuit reverse. Does that sound good or bad?
Back to Top
simonp1100 View Drop Down
Young Croc
Young Croc
Avatar

Joined: 01 September 2008
Location: Bristol
Status: Offline
Points: 1103
Post Options Post Options   Thanks (0) Thanks(0)   Quote simonp1100 Quote  Post ReplyReply Direct Link To This Post Posted: 06 April 2018 at 10:06pm
Try the below things:

1. Have you check transistor isolation between the metal heatsink and the collector (can / case)  of each transistor after you fitted them back in, these should be isolated.

2. The voltage that you are getting on the speaker output, is it a positive reading or a negative reading (with negative of your meter going to the ground) & also what is the voltage across each main power supply cap ???.

3. Check each output transistor emitter resistor (R22 ohms). Check ALL diodes on BOTH boards

4. They is also a +15 & -15 volt supply that is going from the main board to a small daughter board via two 1K wirewound resistors to supply a op-amp, is this voltage there ??? (measure across each zener diode (15V approx) or if not each 1K wirewound resistor on one end should have 15V approx

5. What is the chip number ???.




Edited by simonp1100 - 06 April 2018 at 10:11pm
Back to Top
AJordan View Drop Down
Young Croc
Young Croc


Joined: 06 July 2007
Status: Offline
Points: 1013
Post Options Post Options   Thanks (0) Thanks(0)   Quote AJordan Quote  Post ReplyReply Direct Link To This Post Posted: 06 April 2018 at 10:20pm
Will try all those after work tomorrow and report back Smile

Back to Top
MattStolton View Drop Down
Old Croc
Old Croc
Avatar

Joined: 04 September 2010
Location: Walthamstow
Status: Offline
Points: 4234
Post Options Post Options   Thanks (0) Thanks(0)   Quote MattStolton Quote  Post ReplyReply Direct Link To This Post Posted: 07 April 2018 at 2:52am
When reinstalling the O/P mossies, did you put the right one in the right place. PNP Vs NPN (mossies gates drains mewh, but you get my point)
Matt Stolton - Technical Director (!!!) - Wilding Sound Ltd
"Sparkius metiretur vestra" - "Meter Your Mains"
Back to Top
Muckerbarnes1 View Drop Down
Old Croc
Old Croc
Avatar

Joined: 20 March 2010
Location: Stroud
Status: Offline
Points: 2654
Post Options Post Options   Thanks (0) Thanks(0)   Quote Muckerbarnes1 Quote  Post ReplyReply Direct Link To This Post Posted: 07 April 2018 at 7:04am
It's 2x NPN bipolar as in the OP. No FETs. 

The fwd test on the BR of 0.7 and nowt in reverse;
Was this the same on all 4 diodes in the BR? 
Billy Dawg.
Back to Top
 Post Reply Post Reply Page  <1234 5>

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.06
Copyright ©2001-2023 Web Wiz Ltd.

This page was generated in 0.113 seconds.