EICO HF-89 rebuild help

[mikemakeswine]

I am a complete novice. looking for help on replacement parts. I notice the thread with parts recommendations for HF-81. Are they the same? any help would be appreciated.

 

[Eli Duttman]

The HF-89 schematic is here. The HF-81 is different.

 

[rayma]

I am a complete novice. looking for help on replacement parts.

Do you have soldering experience and the proper equipment?
Does the amplifier work normally now?

 

[audiowize]

You can also post where you are, someone may be able to help you with it.

A buddy of mine bought an empty HF-87 chassis and Heyboer is winding some new transformers for it so we can bring it back to life.

 

[mikemakeswine]

I have soldering experience and can read a set of plans its more about the choice of replacement parts.

 

[Alllensoncanon]

Are they the same?

Beside both use push pull on output, everything else is pretty much different. You might as well start off by asking what you like to fix or improve? BTW, nice amp!

 

[audiowize]

I have soldering experience and can read a set of plans its more about the choice of replacement parts.

Are you flipping it or keeping it?

 

[mikemakeswine]

I'm keeping it. My father In-law built it in 1960

 

[Eli Duttman]

I'm keeping it. My father In-law built it in 1960

OK, Carbon composition resistors drift in value and go noisy over time. Replace carbon comp. resistors, except in grid stopper positions, with carbon film parts of = or greater wattage rating. Electrolytic capacitors literally dry out over time and should be replaced. Panasonic and Nichicon are go to brands in 'lytics. Replace the signal caps. with a mix of 716P series Orange Drop film parts and Soviet surplus K40 paper in oil (PIO) parts.

The OEM B+ diodes are noisy. Replace them with quieter UF5408s. Full wave bridge rectifying the C- bias supply with 4X Schottky diodes is (IMO) a reasonable action.

Unless they have physically deteriorated, leave wirewound resistors be.

63/37 Sn/Pb eutectic solder is good enough, but you can consider some silver bearing alloys.

Most of what you need can be sourced from Mouser Electronics. Flea Pay is a source for the K40 PIO capacitors.

 

[kcdonahue]

It may be helpful for you to search for threads discussing the eico HF-87 since that model is a little more common. Their schematics differ since the 89 has fixed bias and different output transformers but the basic layout of the amps is the same.