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About oldguide

  1. D-150a wiring and parts questions

    I did manage to get rid of the short, but assuredly it damaged some components. At some point I will probably go through and measure all the values to be sure which components are in spec. The driver transistors were the one part other than the op amp I did not replace as they are $6 each. I am a little peeved in that I checked the Crown site to see if a manual was available before buying the 150a They list a 150 manual "all," but it is clearly NOT for all and they should not list it as such. If you are going to have documentation on a support site then it should be accurate as to what it is for. I would have never bought the 150a knowing what I know now. That is what drove me crazy looking for the connection point for the green wire as it does not appear on any diagrams or schematics I have seen nor does that third 10k resistor. Also, as I mentioned, based on resistor values on the board, they are different than in any diagram which leads to an unanswerable question--did someone put in a resistor that the wrong value or is the value right but just not in the documentation? It still would have been neat to see what it sounded like with up-to-date components. Judging by the web there just aren't that many people into rebuilding the 150a. Your help was most appreciated. You certainly went the extra mile.
  2. D-150a wiring and parts questions

    It's dead! Shows a short somewhere, but I cannot find it. When I started checking stuff I realized when the cap and resistor blew they took out part of the tracings on the board. Tried to improvise repairs, but I suspect they may have contributed to the short. May have also burned out more parts. Anyway I've spent enough time on this one. Will pull all usable parts and use it for a nice boat anchor. If Crown had a decent schematic and board layout for the 150A I might be moved to further action, but without knowing what it should look like trying to fix it is like shadow boxing. Potential users should steer clear of this model because of the lack of sufficient documentation.
  3. D-150a wiring and parts questions

    This would have been a lot easier had I left the Grinch green resistors on the board AND if I had an accurate wiring schematic, however, with your great help I think I managed to locate the spot. There is a tiny island just south of the pair of electrolytics with two holes. It is to just one side of the bias adjustment. The resistor runs from one hole to the island with the lower electrolytic. This island is not on the wiring diagram or the diagram of the foil board. I always keep my pulls until I am done and found three Grinch 10Ks, so I knew there had to be another 10K somewhere. The parts list has three 10ks, the third labeled R11. Unfortunately I never was able to find R11 on the board. So I started looking for a misplaced resistor, figuring it had to be a 1xx value. What happened was that when I pulled the 10Ks, I must have been short one and grabbed another resistor which was a 100 ohm (those stripes will get you). I found a 100 ohm I knew it had to be wrong wince the resistor list does not have a 100 ohm. The place where that resistor was located seemed the most logical. It puts one 10k almost perpendicular to the other. Does that make sense? I'd love to see someone post a 150A schematic and wiring diagram. I decided to go ahead and assume that was the right spot since nothing else seemed logical, so after a couple of hours checking everything and cleaning up some solder mistakes I slowly increased the voltage. The one problem I have now is that the IOC light on channel 1 will not go out. I checked all the possibilities in the troubleshoot but all check out OK other than the op amp which I have no way of testing--although I would not think the op amp would be bad only in one channel. Take care.
  4. D-150a wiring and parts questions

    Thank much for all that info. I did not think the 22uf vs 22uf made any difference, I was just curious as to why there would be the inconsistency in the Crown materials. I caught the NP on those caps after I had already picked up some polarized ones. I think its just a habit of always ordering the polarized. As for the green wire, there is an empty tab between the 10K resistor and the 510 on the same section of foil. It looks like there might have been a wire there. So do I solder the green wire there or, do I connect directly to the 10K? I assume we are both talking about the right side of the foil side as the wire seems to have come from there judging by its length and position. I also see in the block wiring diagram that it goes to only one side, Having a series II would have made things a lot easier. My tactic has been to just replace one component at a time and match the value of what was there. Maybe I bit off more than I should, but I figured if I was going to pay shipping for parts I might as well buy replacements for the others since the resistors and caps are fairly inexpensive. I've played quite a bit with the Dynacos, but this is another order of magnitude, although by and large the board is nice and solid. I am hoping once I get it running again that the op amp is OK as I have not seen any parts sources for it. Should the big can caps be replaced or do they tend to be pretty solid? BTW, I wish I were on the UK side of the pond, but am over in the US. Your offer to phone you up was much appreciated. It would be great to get it going again as even the hard-to-convince wife admitted it had a great sound. Take care and thanks much.
  5. Just acquired a used D-150a which sounded great for a few weeks and then started distorting intermittently. When I cracked it open I found the green wire from the stereo/mono switch had worked loose and I have no idea where it goes. The wiring diagrams do not show it. Any help from other D-150 owners or Crown techs would be appreciated. The schematic shows some of the wiring but not all. Is there are schematic available that shows all? None of the wires from the switch are in the diagram. Also there is an orange wire and a couple of others not in the diagram. The other thing I found was that the 10uf cap was leaking and the R3 looked like a firecracker about to explode. So the other questions concern inconsistencies in the values for several caps and resistors. Caps 108,109,208,209 are listed in the parts list as 22uf and in the diagram as 25 uf. Which is correct? Judging by the color coding, several resistors also are different than in the parts list. I will assume this is because someone replaced them with whatever was at hand with the closest value. Finally I suspect the diagram is for the series II, as there are a few resistors in my amp that are not even in the diagram. Kind of fun working with a diagram that is essentially upside down--i.e. from the foil side. I can understand the reasons for that, but you really should have both views. Gives you headache after awhile. Only blowing it up on my computer screen saved my eyes. I figured as long as I had it open I would recap and replace resistors that were out of spec and also replace transistors and diodes The wiring also is pretty brittle--hence the broken green wire, so I am replacing that with Teflon coated wire I have from other projects. When I am done I will have a D-150a with up-to-date parts. Be interesting to see how it sounds with new parts. Am driving it with a modded Dynaco tube preamp into AR3 speakers. Stumbled across Crown when one of the old AR techs recommended it for driving the ARs. Thanks for all your help. Great sounding amp and hope to have it working again.