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Pat 4
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Here is a fresh Pat 4 as a candidate for rebuilding. This unit was a kit unit and was carefully assembled but the owner which makes this rebuild a much easier task. Some kits that are not as carefully built have wires too long or too short.  In the case of the wires around the Selector switch this is a problem as they are solid wire and can easily damage the switch during any operation to correctly place the wires.
This is another unit that was kit built and had a lot of wiring problems. Many cold solder joints, wires that were stripped at the end in a process that actually cuts through the wire and as soon as I touched the wire in some cases it broke off. Many wires had to be shortened and moved to keep them dressed away from parts of the circuit.  At this time you can see the new Non-Polarized capacitors feeding the tape out and the from the front panel input jack. Also at this time all switches are cleaned, as well as pots.
This is a close up of the rear panel jack strips. You can see the new caps and the new terminating resistors. You can also see the new shielded cable feeding the output jacks for output #1 and #2.  This is the stage were the first of the multistranded copper ground wires are installed for the new modified star grounding system.
Here is a detail of the selector switch. You can see the mil spec mini co-ax cable used for the phono inputs. To the left you can see the PEC board that has the resistors and caps for the high and low level phono input as well as the ceramic or crystal phono cart input.  In a full upgrade these are replaced with 1% tolerance parts newly build right on the input jacks.
These two boards have had all the electrolytic capacitors removed and replaced with non - polarized ones where available.  In the full upgrade all caps are changed to noin-polarized items. In these boards you can see the metal film resistors replaced in the phono and equalizer sections. Again in the full upgrade all the resistors are changed to metal film replacing all the carbon composition items. Original feedback and equalization caps are used as they rarely go bad. If the phono section fails to pass the RIAA curve when finished, the caps that have failed are replaced.  If you wish for an extra $15.00 these can be replaced at the time of the upgrade.
This is a board modified with all non-polarized capacitors replacing the original electrolytic caps. You can see they are larger units and due to availability not all cps in all upgraded boards are the same brand but all are high quality.  Notice all resistors have been upgraded with replaced metal film units.
Two pc boards back on the brackets and ready to go back in the chassis for final wiring.
This is one finished unit with non polarized caps, all metal film resistors and  a new power supply cap boards.  I always use at least 1000 - 1000 - 2200 or large depending on availability.  In the full upgrade they are then bypassed by a 10uf non polarized capacitor and a 1uf polyester capacitor as well.
This was not a full upgrade but has the modified grounding . The advantage of a star system is that all the ground returns for the pre amp are returned to the same place with no return current going through the chassis. In the Pat 4 this is not 100% possible with out a major re-wire of the back panel jack strip.  In this upgrade that is the only place the chassis is connected to ground.  It is connected by multi stranded copper wire from the ground lug by the phono input jacks, the out put jacks and then the ground terminal on the power supply terminal strip and then the negative of the power supply.
Finished sweet little PAT 4.  This was one of the nicer units I had the pleasure of rebuilding. The sound is marvelous.  Much tighter bass response, more detailed highs and I think a better sound stage.  I do not bypass the tone controls. When they are in the center on the PAT 4 they are our of the circuit. I also feel that with all the different audio mastering done in the last 50 years, it is needed anyway.  A 78 from the 50's album from the 60's and cd's from the 80's and 90's are all produced with varying degrees of sonic quality.
Back jack panel of the PAT 4. All the RCA phono jacks are cleaned and burnished.  If you are wondering about  them and if gold connectors are better, they are. However you will need a very very good system to hear that kind of difference and if you have that system you should be using a higher end pre-amp anyway.
Front panel of the PAT 4. Still one of the best looking and functional units that you can use today for a variety of source material. When playing a mono record with a stereo pickup you have the choice of either channel or both.  the rumble filter works well but I hope you have a good turntable and do not need it. The high filter is one of the best and I use it with cassette and older reel to reel tapes.



Copyright (c) 2007 R. David Adams. All rights reserved.