On 16 nov, 16:50, kvm wrote:
b wrote:
On 15 nov, 04:21, kvm wrote:
b wrote:
these two vertical output ics seem almost identical, i think the 8170
needs a ref voltage on pin 1. can they be interchanged? if so, what
mods if any will be required.
cheers. B
TDA8177 ICs are getting hard to find (discontinued).
Why not use it's smaller counterpart. The TDA8172 is a drop in
replacement that works for me. I have replaced 8177s with 8172s in
commercial 25" RGB monitors with no failures (2+ years) (Dotronix
DSV-25C video wall monitors). There should be a electrolytic capacitor
just off of the pins of this IC. It is usually a 100mfd with a voltage
rating between 35v and 50v. Replace this cap or you will be replacing
the IC again. (I use a 100mfd/63v which cuts down on failures).
No extra circuitry changes are needed if going from 8177s to 8172s. The
worst that can happen is the IC fails. I have used this IC in Toshiba
projection units also with no failures.
Good luck!
Dave

Hi Dave
thanks a lot for the info. I actually picked up a couple of TDA8177
from my local supplier for about 2€ each. Have yet to test the set
extensively but I did replace the IC and cap you said, and two 1000uF
16v caps providing a +10v and -10v to the ic (used 35v 105º types).

coincidentally I now have another set to fix, with a similar fault,
only it uses a TDA8178S - do you think the TDA8172 would work there?
the TDA 8178S is more expensive, at least in my local store. Ben

B,,
You might want to do a google search of TDA8170, 8172, 8177, 8178.
search as "TDA8172 pda" etc. You will find that the TDA8178 has a much
higher working voltage than TDA8170 and TDA8172 (90V) but lower current
handling (2A). There is a wealth of information available on the "net".
I think I'd spend the extra "pounds" and get the right IC as the working
voltage in the circuit would probably kill a lower voltage rated one.

Lots of great info on the net... Just remember to replace the "pump-up"
capacitor (100mfd/63v) as this is usually what causes the death of
these ICs.

Lots of luck!
Dave

thanks again Dave. I have got the datasheets now. and will follow it
up.
I just checked the set in which I changed the TDA 8177F, the pumpup
cap would appear to be 33uF. I suspect a slightly higher value may
have been wise for reliability, who knows. reminds me of the vestel
11AK30 chassis line drive decoupler which is 10uF and many techs I
have spoken to replace it with a 47uF, since things run cooler that
way.
-B