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Dynaco PAT-4 from electronics recycler, will it match well with a Hafler P-225?

sunvalleylaw

sunvalleylaw

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Got this little guy for 39 bucks from the local Boise computer and electronics recycler/thrift store. the note said works but has scratch tone pots. I figured I could fix that and was interested. Seems clean inside and out and a little CRC QD has the pots moving well. I don't have time tonight to connect it to anything, up past bedtime now, but wondered if this might work nicely with my Hafler P-225 which is just the "pro" version of the DH-220. It is currently on the bench needing a repair but seems like it might. I do have a little Mitsubishi M-A4200 I can also try it with that I also got from the same place for 40 bucks. Might be fun to try! Anyhow, if anyone wants to tell me some things I should know about this preamp, let me know!

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Should be just fine. The hafler can likely handle a hotter input, if you find yourself maxing out the pas volume to get where you want then the answer is no. But try, probably sounds good.
 
sunvalleylaw said:
Got this little guy for 39 bucks from the local Boise computer and electronics recycler/thrift store. the note said works but has scratch tone pots. I figured I could fix that and was interested. Seems clean inside and out and a little CRC QD has the pots moving well. I don't have time tonight to connect it to anything, up past bedtime now, but wondered if this might work nicely with my Hafler P-225 which is just the "pro" version of the DH-220. It is currently on the bench needing a repair but seems like it might. I do have a little Mitsubishi M-A4200 I can also try it with that I also got from the same place for 40 bucks. Might be fun to try! Anyhow, if anyone wants to tell me some things I should know about this preamp, let me know!

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Checkout the link below for restoring and updating your PAT4.
I had one some years back and the preamp board upgrades and slight mods made a big difference for the better.

Update My Dynaco

Updatemydynaco makes audiophile kits that make your Dynaco Stereo 120 Power Amp or PAT-4 Preamp even better than new.
www.updatemydynaco.com
 
Lavane said:
Checkout the link below for restoring and updating your PAT4.
I had one some years back and the preamp board upgrades and slight mods made a big difference for the better.

Update My Dynaco

Updatemydynaco makes audiophile kits that make your Dynaco Stereo 120 Power Amp or PAT-4 Preamp even better than new.
www.updatemydynaco.com
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Thanks! I’m definitely going to need to put some more work into it. I forgot to clean the switches when I did the pots last night so that might be some of it, but I’m getting a bit of distortion. Currently hooked up to the power section of this Yamaha backup amp I have. And into ADS mids I used for backyard speakers over the years. IMG_0546.jpegAlso, I did not clean out the inputs and I’m wondering if I might want to do that too. But, it might need some other restoration or upgrading to get the best out of it. It is the first piece of Dyco equipment I have owned and I like that quirky old stuff so this is a fun low cost entry to messing around with some of it.
 
sunvalleylaw said:
Thanks! I’m definitely going to need to put some more work into it. I forgot to clean the switches when I did the pots last night so that might be some of it, but I’m getting a bit of distortion. Currently hooked up to the power section of this Yamaha backup amp I have. And into ADS mids I used for backyard speakers over the years. View attachment 3832663Also, I did not clean out the inputs and I’m wondering if I might want to do that too. But, it might need some other restoration or upgrading to get the best out of it. It is the first piece of Dyco equipment I have owned and I like that quirky old stuff so this is a fun low cost entry to messing around with some of it.
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Once sorted out its not a bad preamp. There are the basic thjngs that need done like a recap, but tye preamp board kits make it a better preamp. If I remember right one of the parts replaced on the preamp boards is a transistor to replace the original. It looks like whoever built that one did a pretty good job.
I've seen some that were a real mess.
 
Lavane said:
Once sorted out its not a bad preamp. There are the basic thjngs that need done like a recap, but tye preamp board kits make it a better preamp. If I remember right one of the parts replaced on the preamp boards is a transistor to replace the original. It looks like whoever built that one did a pretty good job.
I've seen some that were a real mess.
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Swapped out the speakers for some Min 7's and played with the high cut filter and it is sounding better now. But yeah, this will be a fun little project to figure out and do, and as I am a beginner to re-capping and modding, other than some really really basic repair stuff, it will be a nice piece to practice with. I will go look for an upgrade kit and start to research that. Let me know if you already know of a really good one. This does sound like it has real potential for a fun little unit.
 
I think I worked on the pat4 or 5 (or both). I thought a simple ps caps and coupling caps was enough.

Some like the 5 more but I liked the 4. Can't recall the difference.

I probably used a hafler 200 or dynaco st-150.

Looking forward hearing your thoughts on the Mitsubishi.
 
rickl said:
I think I worked on the pat4 or 5 (or both). I thought a simple ps caps and coupling caps was enough.

Some like the 5 more but I liked the 4. Can't recall the difference.

I probably used a hafler 200 or dynaco st-150.

Looking forward hearing your thoughts on the Mitsubishi.
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Well, it was sounding decent, but then blew it self up with that nasty smell, so pulled it. Didn't have time to look at it for now, so goes in the "to be fixed" pile for now.
 
I just rebuilt a PAT-4, replaced all of the axial electrolytics with Vishay axials from Mouser and Digikey. Checked all voltages per the assembly manual, they were spot on.

This preamp sounds really nice, it's a bit livelier sounding than my rebuilt PAS-3.

If I had a PAT-4 that was trashed, I may consider updatemydynaco but I wouldn't gut a clean example that only needs to be freshened up.

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malden said:
I just rebuilt a PAT-4, replaced all of the axial electrolytics with Vishay axials from Mouser and Digikey. Checked all voltages per the assembly manual, they were spot on.

This preamp sounds really nice, it's a bit livelier sounding than my rebuilt PAS-3.

If I had a PAT-4 that was trashed, I may consider updatemydynaco but I wouldn't gut a clean example that only needs to be freshened up.

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The slight changes to the preamp boards with the one small upgrade kit is worth the effort. And its easily reversed if you decide to sell it.
If your resroring it to re-sell then, ya, keep it in stock form.
Dynaco sold so many kits and it isn't like these are rare or anything.
The single transistor swap for the preamp stage, and the small kit for the phono stage does lower the noise floor and distortion. The difference is noticable at higher volumes. I wouldn't go for the completely different boards they sell though. That will turn the PAT-4 into a completely different animal. Like the difference between the Dynaco ST-70 and the Tubes4hifi ST-70.
The Tubes4hifi ST-70 and Mklll driver boards turn those amps into something completely different.
 
Lavane said:
If your resroring it to re-sell then, ya, keep it in stock form.
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I rarely sell gear that I restore

Lavane said:
Dynaco sold so many kits and it isn't like these are rare or anything.
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I have several, so yes, they are not rare

Lavane said:
The single transistor swap for the preamp stage, and the small kit for the phono stage does lower the noise floor and distortion.
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my stock PAT-4 is dead quiet and it sounds as good as any of my preamps.... Maratz 3200, Hafler DH110, Adcom GFP-565, Apt Holman, Dynaco PAS-3,
 
malden said:
I rarely sell gear that I restore


I have several, so yes, they are not rare


my stock PAT-4 is dead quiet and it sounds as good as any of my preamps.... Maratz 3200, Hafler DH110, Adcom GFP-565, Apt Holman, Dynaco PAS-3,
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I had collected and restored a lot of Marantz seperates from the 70's.
I had a 3200 and the TOTL 3600. I actually thought the little 3200 sounded better than the TOTL 3600. I had the earlier model 33 and 3300 preamps as well. The The later preamps after the 3300 had deviated from the original house sound by then though. If you ever got the itch for a Marantz 7T preamp, the 33 and 3300 sound very close to the 7T and for less $$.
I sold off all but three pieces of Marantz gear when I switched to tubes.
The tube preamp in my main system has a problem after eight years of use, so I'm using my Marantz 1060 integrated amp as preamp for now. Its one of my favorite Marantz pieces. When restored it sounds really nice for a cap coupled amp, but it makes a great preamp too.
 

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The Rocker Switches can be a problem. Clean them 3 times! The can cap will go out soon - at least change that. If you have any hum or crosstalk that can be helped by moving the wires. Example: the wires that go across to the volume and balance pots can be bent to go straight up from their board connection and cross to the pots as close to the metal chassis as possible, etc... Don't move them for no reason - they can break off - but if you hear a problem run it with the top off and see if moving them slightly gets rid of some noise floor. It's free.
It is a decent unit.
 
Lavane said:
so I'm using my Marantz 1060 integrated amp as preamp for now. Its one of my favorite Marantz pieces. When restored it sounds really nice for a cap coupled amp, but it makes a great preamp too.
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My 1060 needs work but I have also used an early Kenwood integrated as a pre-amp, the sound is really great. So much great gear gets little attention by the masses
 
malden said:
When I restored my PAT-4, I measured the can cap for capacitance and esr, it tested within spec. I then measured all of the voltage per the assembly manual and they were in spec as well.
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So did mine but after daily service (on 24/7) for about 2 months it developed a 120hz hum. Here is how the experience went for me:
Refugee

Thread 'Dynaco Pat 4 preamp hum - Replace multi-cap'

Quick project:
My Dynaco Pat-4 preamp started humming. I decided to change out the main filter cap in the power supply. I did not want to spend much time/money on this so I did not obsess on the purchase of a multi-cap that matched well as I usually do. I also did not use a terminal strip for mounting.

I used three Nichicon 1000uf @ 100V caps to replace the multi-cap. The original was 850/700/700. I removed the old cap and slightly bent the mounting ring to accept the three new caps. The caps were faced so that the negative leads were close and twisted together. A random stranded copper...
  • Refugee
  • dynaco dynaco pat-4 multi-cap replacement pat 4 repair
  • Replies: 1
  • Forum: Solid State
  • Like
 
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