Restored A Liquid Seepage Spoiled AHUJA Power Amp Model DPA770
This Ahuja Personal Power Amplifier was brought to me with the complaint that there was no output, even though the USB/FM was working and it was reading the USB. I opened the set and subjected it to a thorough cleaning, as it was reported to be left unused in a Petrol Bunk for a very long time.
Afterwards when I powered on the set, connecting my external testing speakers, the sound was detected to be coming from the Amp section, but not from the USB/FM or other Mic inputs. Traced the wires and found that the pre-Amp board was fit on its side. Fed an audio signal to the point where the input wire was soldered and found it was not coming out.
On a close inspection of the board with a powerful light, I could notice seepage of some acidic liquid, which had corroded and eaten away the tracks.
On enquiry with the customer, they informed that one of the staff in the Petrol Bunk had accidentally spilled butter milk while taking lunch sitting nearby. Well, as we all know, it is an acidic liquid and that is how the tracks got corroded and eaten away. So, wired it up externally and the audio was working fine when tried. Cleaned the board thoroughly with IPA and looked for any more damages.
I also injected audio signal and checked all inputs. Cleaned all controls using switch cleaning oil. Allowed the set to run for several hours before closing the cover and calling the customer to come and pick up. A job finished quicker than envisaged and satisfaction got added to its collection bag too soon! Here are some more pictures:
This article was prepared for you by Parasuraman Subramanian from India. He is 70 years old and has more than 30 years’ experience in handling antique equipment like Valve Radio, Amps, Reel Tape Recorders and currently studying latest tech-classes conducted by Kerala State Electronics Technicians’ Association. He has done graduation in BBA degree, private diploma in Radio Engineering and retired as MD of a USA company. Presently working as Consultant to Hospital and other institutions.
Please give a support by clicking on the social buttons below. Your feedback on the post is welcome. Please leave it in the comments.
P.S-If you enjoyed reading this, click here to subscribe to my blog (free subscription). That way, you’ll never miss a post. You can also forward this website link to your friends and colleagues-thanks!
You may check on his previous repair article below:
Albert van Bemmelen
December 26, 2020 at 6:10 pm
Nicely -with those new arrows- done repair! And good thing that it only involved fixing the broken tracks and cleaning of the inside circuits without having to replace any of the components including the e-caps.
December 26, 2020 at 9:03 pm
Many thanks, dear!
December 27, 2020 at 10:28 am
Dear Mr Subramanian,
Firstly I would like to thank you for your writings. Every time you present an AHUJA repair article It takes me 50Y back to my trainee period in Sri-Lanka. In the latter part of 1960 AHUJA been introduced to Srilanka by a gentleman called M BABU (Brother of BALAJI) from Kerala India. Mr BABU was the then manager Robert Agencies PTY LTD, leading electronics company in Srilanka. I left the company in 1980 to do my own. During my carrier in this company, Babu helped me immensely. Robert Agency has been sold and Babu left the company probably in 1981 and I lost the contact. I heard Babu left the country to live in America. Now he must be in his late 80's. Mr Subramanian, would you be able to track Babu's whereabouts. Ahuja India should know this guy very well. Currently, I live in Australia and I found the former owners of Robert Agency (deceased Grace Somasundaram from India) also live in Aus. Unfortunately, they have no idea of Mr Babu. Please help me.
December 27, 2020 at 1:29 pm
Oh! Very nice to hear this! Glad to learn your interests! Let me try. But I may need his full name and initials! Did you try to trace in Facebook?
Henrique J. G. Ulbrich
December 27, 2020 at 6:09 am
Well done, Parasuraman. It´s amazing that this time you didn´t replace any electrolytic capacitor!
December 27, 2020 at 10:37 am
Yes, I was expecting someone would comment on it! The customer was in a terrible hurry to get it up, as they needed the AMP for a Hall, where their Amp had failed. So, I just checked the ESR of a few main caps, which were within the limits and let it go as it was. I have cautioned the customer that the liquid seepage and lack of preventive maintenance would cause another failure sooner or later! They were ready to take a risk!
December 27, 2020 at 10:54 am
Another repaired set added to your collection bag.
December 27, 2020 at 1:23 pm
December 28, 2020 at 3:05 pm
Well done! Sir
December 29, 2020 at 1:01 am