HA3500a with a very hot Heatsink

[Janou]

Hello :)

I have somes query about an Hartke HA3500a.

It's a long story because i repair it, before use, the main transformer and somes 1N4007 are dead. Very low protection if something happen after the secondary of the transformer.
http://basstock.free.fr/tofs/toro1.jpghttp://basstock.free.fr/tofs/toro2.jpg

In same time i make a upgrade with new OP-Amps, new condensators, new fanLink ( in french sorry ) (http://onlybass.com/html/mod-hartke.html)

The amplifier work very well, have a great sound, i made somes tests with others high end amplifiers, and it's really a good amp now, but i have one and just one little problem. I find with this version ( HA3500a ) a new regulator around the other regulators. It's strange because i already check "old" version and i find two regulator ( the schematic is clear ) with a very little headsink for each regulator, and now i find a big headsink for all of these. Normaly not a problem, but after 10 minutes of use, this headsink is very very hot. It's simple i cannot put a finger more than 5 seconds.
http://onlybass.com/images/ampli/hartke/big/12.jpg
( at the left of the picture )

First, i think OP-Amps ( OPA2604 *1, OPA2134 *8, LT1058 *3 ) stress these regulators, but i find ( i haven't check with ampermeter clamp ) less 200mA of total curent with these new OP-Amps.

I don't have the schematic of the HA3500a, the schematic of the HA3500 is very simple to find, but this one, not really.

What can i do ? Remove regulator and check with ampermeter clamp, check somes voltages ?

Thanks a lot for the help :)

[52 Bill]

Welcome to the board!

There are two parameters that you need to check on to see why the regulators are getting hot: Current flow and the voltage drop across the regulators.

When you replaced the transformer, did you use a factory part?

[Janou]

Thanks Bill :)

Yes, the transformer is a factory part, it's not a custom part but it possible that this transformer can use in other Hartke product.

I check these parameter in few hours and come back here :)

[Janou]

Voltage are normaly OK

7805CV, input 11.26v, out 4.98v
7815CV, input 26.2, out 14.6v
7915CV, input -26.2 out -14.9v

I need to unsolder all regulator and check the curent flow now :)

[Gtr_tech]

I wouldn't get too worried about it if its just the 15v regs. If you run it without the cover on the fan can't draw air through the chassis and everything will run hotter. The fan will move enough air around to keep everything happy.....just put the top back on.

[Janou]

:) I make all test with cover on the amplifier, just after 10 minutes, i remove cover and check the headskin, and it's really warm.

For all mesures i keep maybe 20 seconds for each regulator. I need to test current flow and after if the values are OK, it's OK for me :)

[Janou]

I check all curent flow 10 seconds after the power on of the apparatus for each values.

7805CV, input 11.26v, out 4.98v Current flow input 0.36A, out 0.36A
7815CV, input 26.2, out 14.6v Current flow input 0.20A, out 0.18A
7915CV, input -26.2 out -14.9v Current flow input 0.21A, out 0.21A

I check with a multimeter with 20A range. Values seems good, but the headsink is really hot, it can make breakfast :)