Refreshing Older Hafler Amp...

jakelm

Helps a bunch elg...Thanks for all that info.

I understand you in saying that all of the caps were puchased from Mouser?

I did replaced the switch last year and went with a larger disk cap to prolong the life of the switch.

Again..thanks and welcome to Polk..if no one has given you a welcome yet.

jakelm

When I run no signal to the amp. And turn the vulume up, I can here static from the left chanel. Is this a MOSFET going bad or a ground problem?

jakelm

Copy and paste.... You cant beat that...Wow

See how easy that was....lol

Thanks again elg..:D

jakelm

What are these called? They look like antennas.

elguapo99

Those metal objects are heat sinks on the various transistors.

jakelm

Thanks elg.

I wanted to ask, what should we call you? Elg? or is there another name you would prefer?

jakelm

I assume it comes from The Three Amigos...lol

elguapo99

I've been called worse. Yes, it is from Three Amigos and 99 was Gretzky's number. My name is Bob. As a previous poster recommended, the DIY audio forum has a very lengthly thread on mods for the DH-200. Some are easy to understand and some are not. I have performed most of the easier one's that I could understand such as bypassing the input caps and filter caps and adding a resistor to the filter caps. The DH-200 is relatively easy to work on so you shouldn't have much trouble. Be careful and make sure that the large filter caps are fully discharged so as not to get zapped. What preamp are you using ahead of the DH-200? I am using a DH-110 which I have also recapped. Good Luck.

jakelm

Its a cool name..I love the 3 amigos.

Yes I have read throughmost of DIYaudio's dh-200 mods. Most of it was way over my head. But nice people there, they helped me change my switch and recommended a high cap value for the power on spark. Which came out very well.

I have a HK635 as Pre/Pro. Awsome AVR, I would recommend the HK to everyone I meet. It has almost as much power as the Hafler.

This is all new to me, I'm used to upgrading crossovers and simple repairs. Never jumped into full refresh. But I think this amp is absolutly prefect for anyone who wants to learn about electronics.

The guys at DIY are very harcore about the 200, 220 and 500 (bridging and what not). Way over my head on most of it.

You help me greatly. I was hoping someone would chime in and say "look, I changed this this and this, with this this and this".

My next step with this amp is learning how to adjust the bias. The trimpot is clearly marked where it need to be. But turning it left or right is still a question in my head, so I will leave it alone for now.

Upgrading the outputs and inputs interconnects will come in the very near future as soon as I'm finished with the internal upgrades.


Jake

jakelm

El, did you ever tinker with the power cord? I would like to go with a 3 way cord with the ground. I wonder how that could be done?

jakelm

Any temperature changes with the ugrades?

Systems

elguapo99 wrote: »

and 99 was Gretzky's number.

Yah he was pretty good:D

elguapo99

I replaced my power cord with a 2-conductor cord. I wasn't sure where to connect the ground wire when using a 3-conductor cord. I haven't noticed any temperature changes after recapping my amp.

jakelm

I read that someone in DIY replace the 2 with a 3 conductor cord, and grouded it to the chasis under the PS.

I have to say, the stock cord is a pretty wimpy cord.

jakelm

A common practice and for good safety reasons is to tie the chassis to the groung wire (neutral) of a 3 wire power cord. Protection in the outside chance of a transformer winding shorting or other shorts to the chassis since there is the potential for lethal voltages to be present on the case of the equipment.

Here is where I read it..Page 10 post 237

Systems

Im surprised it didn't come stock with a 3 pronger.

fredv

Most, if not all, of the gears prior to the early 90's used 2 prongs, all my Adcom, Carver, McIntosch are alike in that regard. I suppose that might be a common way to avoid ground loop :-)

Systems

Thats interesting that those 3 didn't use them as some certainly did .My Belles (circa 1982)and Bryston's dating back to the 70's used them.Maybe the UL didn't require their use.

Your point about avoiding grounds also makes sense.

jakelm

I dont know but there is something about that, that doesnt seem right. Every peice of equipment I own , that is up to date (so to speak) has 3 prong plugs. If ground lood was a problem, then they wouldnt have the 3 prong either, unless the amp being ground to the chasis would be the cause.

Systems

jakelm wrote: »

If ground loop was a problem, then they wouldnt have the 3 prong either, unless the amp being ground to the chasis would be the cause.

Use of the 3 prong just means that manufacturers have to do some things differently to avoid ground loops.Such as isolating the input connectors from the chassis and connecting circuit ground to chassis ground through a resistor etc.

jakelm

GV#27 wrote: »

Use of the 3 prong just means that manufacturers have to do some things differently to avoid ground loops.Such as isolating the input connectors from the chassis and connecting circuit ground to chassis ground through a resistor etc.

Which is excatly what Hafler did. They isolated the input and used a resistor to tie to the chasis, on just one input, but both are isolated from the chasis.

jakelm

Parts went in with ease. Havent had a chance to listen to it yet because I have speaker terminals and input jacks for the amp coming in from PExpress.

I want to thank you all for the help you have given me.

Jake