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Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

Hafler Iris preamp repair
Hafler Iris preamp repair
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Old 25th June 2010, 11:06 PM   #1
jb9 is offline jb9  United States
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Default Hafler Iris preamp repair

After many months (OK, years) of dithering about, I finally got my Hafler Iris Preamp repaired. I'm writing this for posterity, in case it may help others in the future.

Unit ran fine for decades. One day in the middle of a listening session the amp blatted a loud hum for a few seconds, then the Iris shut down.

The Iris AC power fuse was blown, and when replaced it blew again after about 3 seconds.

The regulated +16V line measured 0V (in the brief period before the fuse blew). -16V line was fine.

With power off, the +16V line measured a dead short.

Pulling and testing all the chips and electrolytic caps on the main board didn't help.

Narrowed it down to a shorted tantalum cap on the front panel display/push-button board (4.7uF 25V). Replaced it with the same value (I would have used a higher voltage unit if I had one), and the problem was fixed. Getting to this board requires substantial disassembly.

While I was at it, I replaced the main power supply caps with new units just as preventative maintenance.

I never did find a schematic; please let me know if you've got one you're willing to share.

Also, don't forget to remove the batteries from the remote if it's going to sit for months (OK, years) like mine. Even alkalines leak, as I discovered to my displeasure.


I'm sitting here listening to it right now ('Gold, Silver and Dirt' by NGDB, a pristine thrift store steal), and oh this phono preamp is soooo much better than the Adcom GTP500-II I've been using in the interim (which otherwise is a very nice unit in itself).

I'm happy now.
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Old 26th June 2010, 01:07 AM   #2
jackinnj is offline jackinnj  United States
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Hafler Iris preamp repair
Tantalums are prone to catastrophic failure -- the TekScopes newsgroup on Yahoo is full of disasters.
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Old 27th June 2010, 12:58 AM   #3
evanc is offline evanc  United States
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Hafler Iris preamp repair
I have the same preamp. I have the schematic. PM me with your email addy and I'll send it to you (it is too large of a file to attach here).
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Old 28th June 2010, 10:19 PM   #4
georgehifi is offline georgehifi  Australia
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The Hafler Iris has a similar but not as advanced version of my Lightspeed Attenuator, as a volume control, you may want to replace this with my setup as it should also sound much better for it.

Cheers George
Avatar : Production Lightspeed Attenuator
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Old 1st February 2011, 05:48 PM   #5
timthedog is offline timthedog  United States
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My Hafler Iris preamp just died, or at least fell seriously ill. On power-up there may have been a slight audible zap sound coming from the case. The unit lights up and will pass a signal but what comes out is very attenuated, clipped, and distorted. Putting a signal into the CD jack produces this output regardless of which input is selected; this is the same for any of the non-phone input jacks. The volume and balance controls seem to work both locally and on the remote. A visual inspection of the PCB shows nothing amiss, there is no unusual smell, and gently tapping on each discrete component has no effect. Internal B+ voltage is a steady 16v. My only measuring equipment is a VOM. Any suggestions much appreciated.
Jim Gregory
Sausalito, CA
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Old 2nd February 2011, 06:44 PM   #6
timthedog is offline timthedog  United States
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Default Hafler Service Centers?

While I hope to be able to repair my Hafler Iris Preamp myself, as a backup I asked Hafler if they would service the unit. They answered by saying that any one of the following service centers can repair the Iris Preamp. Has anyone experience with any of them?
Landis Technical(NC): 704-575-2134 LandisTechService@hotmail.com
Davidsons(NY): 516-753-0197
Scan Audio(CA): 818-786-4240
Many thanks,
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Old 6th April 2014, 11:32 AM   #7
Techshops is offline Techshops
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Originally Posted by evanc View Post
I have the same preamp. I have the schematic. PM me with your email addy and I'll send it to you (it is too large of a file to attach here).
evanc I was wondering if you were still prepared to share your Hafler Iris schematics?
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Old 1st August 2014, 11:22 PM   #8
Talon is offline Talon
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I'll second that. I think I have a set of schemes here but I can't find them. Evanc let us know if you still have that available!

I have an IRIS preamp to repair here. It turns on and seems ok, but it goes into mute mode and can't be switched out of it. It stays locked in mute even with the IR board removed. There is a specific socket on the main board that says "MUTE" next to it, so I figured I'd start by replacing that. But while I was looking around I counted up all the chips and decided it would be cheap to replace them all, due to age. But then, I started thinking, "Well instead of sourcing NOS pieces, maybe there are better parts out there?"

So... I'd like to upgrade the ICs. This will be my first "hotrod" project, so I'm a complete rookie when it comes to deciding which modern ICs will work in place of the original parts.

the parts list:

MC 3458P1 dual op amp, low power
MC 14051BCP analog multiplexer switch SP8T
MC 14053BCP " " " Triple SPDT
LM 1458N dual op amp, general purpose
LM 3046N NPN transistor array
LM 308N single general purpose op amp
TL 082 dual op amp general purpose

I noticed when searching for info on the TL082, one of the members said that the LM1458 was known to be a replacement for the TL082, but it was noisier. So I have to ask, why didn't Hafler just use the TL082 in place of them? That leads me to believe that there is more to upgrading than just finding the "quietest" part and putting it in there.
Doing a search for replacements is what pointed me to this forum so I hope you folks can offer some advice. I really want to learn this stuff.
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Old 2nd August 2014, 10:01 AM   #9
sgrossklass is offline sgrossklass  Germany
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I would be very careful with op-amp "upgrades" without at least a schematic and a picture of the board layout at hand. You don't want to create a nice little oscillator there. Rail decoupling and layout in units of this vintage may be more than modest by modern standards, surrounding impedances are likely to be highish, and the power supply's current capability is not infinite. Why the individual parts have been picked should become clearer with a schematic at hand.

EDIT: Reading the Stereophile review, this model is about a decade newer than what I would have guessed from the opamps. Looks like it mostly relies on discrete JFET circuitry for amplification, so opamps may be relegated to noncritical tasks entirely.

Last edited by sgrossklass; 2nd August 2014 at 10:22 AM.
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Old 12th July 2015, 04:01 PM   #10
Talon is offline Talon
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sad progress...

The original problem began after a lightning strike that took out my whole stereo. Melted mid woofers in my speakers, blown fuses in my amp, the IRIS tuner stays on "seek", and the IRIS preamp went into "mute" and wouldn't come out of it. I can do without the tuner but the preamp is a must-fix if I want a good hifi system again.

After months of delays I finally had the time to source and replace some of the ICs. Since the mute circuit was the one that seemed to have the obvious problem, I started by replacing that IC (conveniently marked "MUTE" on the PCB) with a NOS LM1458N. I reinstalled the IR card, powered up the unit... and the mute light was still lit, though it didn't seem to have the brilliant light it did before I did the chip swap. I pushed the button a few times to see if it would go out. Eventually it did, along with any other lights. Now I have no working lights even if I power down and back up.

I haven't checked this with a signal yet to see if anything is going through it, but it appears to be dead. The panel lights used to all illuminate in sort of a self test, now nothing.

I don't have a scope, just a decent analog VOM and some continuity lights. I would really like to know what steps you guys would recommend I follow in order to find the defect.
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