using a TDA 8170 instead of a TDA 8177F?

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=80 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 105=BA 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

e

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

The difference in values may have to do with you being on the other side of the pond. Our (USA) scanning frequencies are 60hz vertical and

15575hz horz. I believe your vertical scan rate matches your AC line (mains) frequency of 50hz (at least for analog TV). Check the pump-up caps in a few TVs as this may be the case. I'd be curious to see if they are different. Dave.