Hello from the Orchard

tdickman83

New Around These Parts
Joined
Nov 26, 2023
Messages
12
Location
Central California
Hi All,
Joined the forum a few days ago and have been reading and educating myself. Lots of great info. I have a PL 400 I bought new in 1978, while stationed in Wildflecken, Germany in the Army. Purchased at the Audio Photo Club. Had it repaired once in the 80’s at a shop in CA. It’s been sitting in my basement for 10 years since it started blowing the 5A supply fuses. Started up my basement as a man cave, so thought I would revive all my old equipment, just rebuilt my ESS AMT monitors. I bought an output relay speaker protection kit from wattsabundant. But before I install I think I need to replace some or all the output transistors, both channels are vaporizing fuses. The repair I had done in 80 they replaced 4 transistors, two of them were Toshiba 2SD371, the other two PL909 (i didnt know this then). Anyway looking for advice, should I replace all 12 of the output transistor PL909 and the 4 driver outputs RCA 66546? I followed the instructions in the service manual and ohm’d out each transistor. Column 1 and 2 the PL909 were 10.8 and 11.3 ohms. Column 3 and 4 which had replaced transistors were all about 1 ohm. The driver transistors ohmed out at 211, 242, 278 and 351 ohms.
 

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Leave the 66546's---they are rebranded RCA 410's. Can't do better for a driver. If you have that many outputs blown there is a distinct possibility that
some emitter resistors are blown and possibly the pre-drivers on the driver board are toast. Follow the service manual, it'll get ya through most of that..
And welcome to Phoenix..
 
Welcome!
I love ESS AMT's! I have a variety. My main rig has a pair of AMT 3 Rock Monitors for the front driven by a WOPL 400. Another PL400 drives a pair of Infinity RS with EMIT tweeters and Watkins woofers for rear. Carver C1s feeding both. See Avatar. Great group here with massive knowledge.
 
Hi All,
Joined the forum a few days ago and have been reading and educating myself. Lots of great info. I have a PL 400 I bought new in 1978, while stationed in Wildflecken, Germany in the Army. Purchased at the Audio Photo Club. Had it repaired once in the 80’s at a shop in CA. It’s been sitting in my basement for 10 years since it started blowing the 5A supply fuses. Started up my basement as a man cave, so thought I would revive all my old equipment, just rebuilt my ESS AMT monitors. I bought an output relay speaker protection kit from wattsabundant. But before I install I think I need to replace some or all the output transistors, both channels are vaporizing fuses. The repair I had done in 80 they replaced 4 transistors, two of them were Toshiba 2SD371, the other two PL909 (i didnt know this then). Anyway looking for advice, should I replace all 12 of the output transistor PL909 and the 4 driver outputs RCA 66546? I followed the instructions in the service manual and ohm’d out each transistor. Column 1 and 2 the PL909 were 10.8 and 11.3 ohms. Column 3 and 4 which had replaced transistors were all about 1 ohm. The driver transistors ohmed out at 211, 242, 278 and 351 ohms.


I was in the 2/15th "Top of the Rock" Battalion and in Wildflecken the same time as you. PM me... Maybe we knew each other.
 
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