Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Chip Amps Amplifiers based on integrated circuits

Optimizing TDA7294 Output
Optimizing TDA7294 Output
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 5th March 2017, 11:33 AM   #841
Dirk83 is offline Dirk83
diyAudio Member
 
Join Date: Jan 2017
Default TDA7294 Stereo board Pin issue

Hi,

I have bought a stereo board for TDA7294 with PSU and speaker protection all on the PCB. Sounded like a good starting point for building a first amplifier.
Probably not regarded the top choice here but I have some Motivation to finish it since I have it here now.
With the plentiful Information very kindly provided in this topic and the (kind of) corresponding TDA7293 topic I have tried to reconstruct the circuit.

One thing I have missed initially was that the bootstrap cap is connected to pin12 on this board instead of pin14. I have measured resistance between pin12 and pin14 of the TDA7294 provided and they seem not to be connected. So likely no fake TDA7293 with TDA7294 Label!?
Labeling says TDA7294 V6.

Well, to make a long story short: can I clip of pin12 and place a jumper to connect the bootstrap cap to pin14?

Unfortunately I haven't made a Picture before I started soldering but hopefully the attached one helps (some Details on my understanding of the circuit below). With NFB, bootstrap and power supply bypass provided as 22uF I haven't finished the board but ordered 220uF/63V (NFB, Bypass) and 47uF for bootstrap.

Help would be appreciated! I could also get more Pictures if this is of any help.

Thanks,

Dirk



To the best of my Knowledge:
C3=C8 in datasheed=power supply Bypass
C4=bootstrap cap
C6=NFB cap
C5/C7=mute caps
R1=Feedback resistor
R2=Input load
R3=Feedback shunt
R4=Standbye
R5=Mute

PS: Apologies for my stupid autocorrection capitalizing words all the time...
Attached Images
File Type: jpg Bootstrap path.jpg (959.8 KB, 317 views)

Last edited by Dirk83; 5th March 2017 at 11:41 AM.
  Reply With Quote
Old 5th March 2017, 04:06 PM   #842
Dirk83 is offline Dirk83
diyAudio Member
 
Join Date: Jan 2017
Default solved, it's about the different options for C4

Hi,

by now I have made it. The connection of the bootstrap (pic in post above =C4) can be made via the different positions of C4. Yet, the track is kind of hidden, at least for someone as new to it as me.

Still worth considering to clip Pin12 of the TDA7294 and make connection to Pin14 with a jumper there...if this would work out?
  Reply With Quote
Old 8th March 2017, 11:38 AM   #843
danielwritesbac is offline danielwritesbac  United States
diyAudio Member
 
danielwritesbac's Avatar
 
Join Date: Nov 2007
Quote:
Originally Posted by Dirk83 View Post
Well, to make a long story short: can I clip of pin12 and place a jumper to connect the bootstrap cap to pin14?
On that version of TDA7294, you can clip Pin12.

See TDA7294 datasheet: http://www.st.com/content/ccc/resour...CD00000017.pdf

For current production TDA7294 (both real and fakes), use TDA7296 datasheet: http://www.st.com/content/ccc/resour...CD00000198.pdf
Same news, except for lower voltage. Pin 12 is still "N.C." which means you can cut it off if you need to.
__________________
DIY Models & AppsClipNipperLM1875TDA7293Powerful Parallel TDA7293 kit ♦ My post has opinion.

Last edited by danielwritesbac; 8th March 2017 at 11:41 AM.
  Reply With Quote
Old 24th November 2017, 09:40 AM   #844
Trev0r is offline Trev0r
diyAudio Member
 
Join Date: Nov 2017
hi to all
this topic is too usefull to me and special thanks to diy mans
last year i have a problem with 7294! mid and hi got noisy :| solved by mute: 10K 30K+4007 and 10uf. stupid problem and solution
  Reply With Quote
Old 3rd December 2017, 03:29 AM   #845
NareshBrd is offline NareshBrd  India
diyAudio Member
 
Join Date: Oct 2017
Location: Baroda, Gujarat, India
Default STK Hack

Picked up a Sony HCD BX3/DX3 at the flea market here, for 120 Rupees (about $2).
Display on, no output, most likely the STK 402-100 is blown, and that is unobtanium, as some people say.
I am thinking of putting twin TDA 7293 chips, provided there is room, the heat sink has a fan!
The service manual says +45.5 and -46.4 volts on the STK, which pretty much limits my choices of chips.
I think the TDAs are more reliable than the STKs.

I recently purchased several Philips Powerhouse boxes, turned out to be Matsushita AN7161 power amps, and almost totally Rubycon and Elna caps...for a max. $3, in working condition.
A wash with soapy water, rinse with plain water, open, blow off the dust, spray the pots, check DC offset, and good to go...
I have run some of these with my computers playing MP3s, I need basically amps...can't get much cheaper!
Powerhouse was a series of boxes, dual cassette, tuner, equalizer, mechanical switch for selector... Later versions had a microprocessor for selection.

Last edited by NareshBrd; 3rd December 2017 at 03:56 AM.
  Reply With Quote
Old 3rd December 2017, 04:03 AM   #846
NareshBrd is offline NareshBrd  India
diyAudio Member
 
Join Date: Oct 2017
Location: Baroda, Gujarat, India
One older Powerhouse had NEC uPC 1238 with one changed to TDA 2030A
Had to change both due to high DC output, put a TDA 2030A on one channel and a LM 1875 on the other, problem solved.
Odd thing was the speaker was through a capacitor, should not have let DC through.
Now 20 - 30 mV DC, 2 volts without speaker, enough I think to stop fussing.
  Reply With Quote
Old 3rd December 2017, 04:14 AM   #847
nigelwright7557 is offline nigelwright7557  United Kingdom
diyAudio Member
 
nigelwright7557's Avatar
 
Join Date: Apr 2008
Location: Carlisle, England
Quote:
Originally Posted by NareshBrd View Post
Odd thing was the speaker was through a capacitor, should not have let DC through.
If an electrolytic is reverse biased it can let DC pass through it.
After about reverse bias of 1.5 volts it becomes a short.
__________________
PCBCAD51 pcb design software. 2018 version out now. https://www.ebay.co.uk/sch/i.html?_f...nload&_sacat=0
  Reply With Quote
Old 3rd December 2017, 05:13 AM   #848
NareshBrd is offline NareshBrd  India
diyAudio Member
 
Join Date: Oct 2017
Location: Baroda, Gujarat, India
I changed only the chips, the TDA2030 was reading 17 V DC, the uPC 1238 about 4 V DC
The readings came back to below 50 mV DC after replacing the chip amps, I did not change the electrolytics.
All in all it cost about 400 rupees, a fiver in the UK.
Now I have to build a phono pre amp for it, the new owner, a friend, wants to run his Garrard turn table through it.
Planning a 4558 dual op amp at 14 volts available inside the box, boosting the aux input to feed the existing pre amp inside, again a 4558 or 4560.
His son plugged his 70s Sony amp to 220 volts, it had come with him when he moved from the USA, rated at 110 volts. Died.
Says has a nice red wood cabinet, he will let me see after it has been dug out of a closet...Have to see if it can be made to work. Though if it has those special FETs. ....unobtainium again.

Last edited by NareshBrd; 3rd December 2017 at 05:18 AM.
  Reply With Quote
Old 3rd December 2017, 05:35 AM   #849
NareshBrd is offline NareshBrd  India
diyAudio Member
 
Join Date: Oct 2017
Location: Baroda, Gujarat, India
Photo of the unit:IMG_20170908_164111.jpg
  Reply With Quote
Old 29th December 2017, 12:05 AM   #850
Wavewhipper is offline Wavewhipper  United States
diyAudio Member
 
Join Date: Jul 2013
Has anyone tried a parallel PBTL configuration of TDA7293 ? That would mean 2 sets of parallel master-slave blocks wired for PBTL, 4 TDA7293's. That looks like it would allow 4 ohm operation or higher +- V. The parallel master slave simply uses the output section of a second chip, with the input section disabled and isolated by a pin configuration.

Last edited by Wavewhipper; 29th December 2017 at 12:07 AM.
  Reply With Quote

Reply


Optimizing TDA7294 OutputHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Optimizing the VBE Multiplier fglabach Solid State 54 27th December 2017 07:59 AM
Optimizing active crossover atledreier Multi-Way 27 19th August 2011 03:53 PM
optimizing the VBE multiplier hienrich Solid State 80 29th November 2010 11:25 PM
Interesting linestage optimizing ideas PixelPlay Tubes / Valves 5 23rd June 2008 11:18 PM
optimizing for efficiency Dwiel Solid State 13 10th May 2005 10:31 PM


New To Site? Need Help?

All times are GMT. The time now is 09:50 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki