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  • Recent Posts

    • OK, here is the follow-up so far: My transistor tester came in and I got to testing all of the components that were removed from the plate amp of the RPW-10 that has been giving me trouble.  The tester works really well and is pretty much a must have for someone who does this kind of work all the time.  What I found is that all of the smaller electrolytic capacitors (100uf and less) tested had an ESR that was too high!  Even though capacitance was in specs, the ESR showed that the capacitors had needed to be replaced.  Strangely enough, the larger 470ufv100V capacitor that was removed from the amp and replaced a few weeks ago tested totally in spec. I could not locate the larger 470uf 200V cap---I must have tossed that one when it was removed. I also noticed that the smaller yellow film safety capacitors (104K, 250V) had too high of a ESR value; however, the larger 0.22 uF yellow film safety capacitor tested just fine.  All of the other components tested fine and will be saved for recycling in another project.   That said, I think I may have stumbled on a major breakthrough that may solve my problem: I apparently installed the WRONG output transistors in my RPW-10...which was part of the first wave of repairs to my RPW-10.  While I was preparing the output transistors for testing on the transistor tester, I took the opportunity clean the old output transistors and I got a good look at the printed labels.   What I saw basically made my mouth drop to the floor:  All of the output transistors were NOT the same!!!  😲  When I originally I looked at them early last month, I thought they were all IRFZ14 N-channel Mosfet output transistors, so I ordered a set of 10 and replaced all of the output transistors with IRF214s.  When I got a good look at them last night, I saw that there were only 2 IRF214s.  The other transistors were 2 IRF9Z14s and 1 IRF530 to make the total of 5 output transistors.   I tested all 5 of the old output transistors and none tested bad!  However, the mV value, the Vt, gate capacitance, and RDS were very different between the 3 transistor types.  This tells me that the transistor typess are NOT interchangeable and the fact that I installed IRF214s in all slots (Q7, Q19, Q13, Q20, and Q14) likely explains why my amp is not working and why the switching Mosfets in the power supply are heating up with no input or volume.  I feel like a complete idiot for making that mistake! 😖 However, in my defense, it is really easy to mistake the IRF9Z14s for IRFZ14s because these things are very difficult to read!!!   What I need to know now is which slot takes which output power transistor...can anyone check the output transistors in the RPW-10 and let me know the values for Q7, Q19, Q13, Q20, and Q14?  I ordered some new replacements as it makes no sense to re-install the old ones at this point!   Thanks!!
    • We always use this kind of Baltic Birch Plywood the premium quality. Iran is close to Russia and we have access to this material made by Sveza much cheaper than in the US. there is also Wisa of Finland which is more expensive than Sveza and have that little bit of extra quality.
    • Plywood for sure is far more sturdy than MDF for mobile use, bumps and scratches and the occational rain shower. For a stationary indoor loudspeaker however, it appears that bracing and damping/lamination to be more important. There are differences but they are not that huge. Here is a test conducted by the German magazine Hobby & HiFi. The setup is a dual chamber box with a driver in bisecting wall. A board to be tested was  placed in front of the driver and both soundpressure in front of the box (compared to no board) as well vibrations of the board was measured Vibrations to the left and reduction in sound level to the right. The referense was the 19 mm MDF at the bottom. That result is inserted in the other graphs for comparison. Not much difference between 16 mm MDF, 19 MDF and 18mm Plywood.  Fire retarding concrete chipboard 20mm is better but hard to come by. 28 mm MDF is better but not by that much, 20mm stone is way better, 19mm chipboard is slightly worse than MDF and 19mm blockwood a bit worse than chipboard.   These measurements were made in the frequency -amplitude domain, I have seen measurement in the time domain and they show most effect of bracing and lamination more than the instrinsic qualities of the board.  
    • Well then I guess I can mail you a box of Ammo. Sent from my iPhone using Tapatalk
    • Yes, they are closed!   I tried calling to get torque specs for the screws on K-55Vs and nobody home...    Roger
    • I agree, but I"m sure even Atlas has had to shut down manufacture.
    • No kidding wow. Well I'm sure Parts Express has a pretty healthy stock of the wrong ones for Klipsch applications. LOL.
    • I believe Bob has honest curves about them, but I'm not sold on them having "a dime's worth of difference" vs. older k55's, which are very good. Even PWK felt the drivers with the solder lugs (dual phase plug) only had a "prettier curve" but felt that hearing a difference would be tough.........IF they were not abused, like from a Heresy 1 (padded way down by an autoformer) and not from a commercial LaScala that was abused with big amplifiers.
    • Unless they only produce to order (don't know) there ought to be some out in the pipeline anyway.
    • I had a silver blue 68 and always thought that rear hatch and deck would be plenty of room.  What a disappointment!  😂  Gone for a 69 Mach that I wish I still had.
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