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About dynaco_dan

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  • Birthday 10/04/1946

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  1. Dynacos stuffing replacement!

    Hi there Here is my 2 cents worth of advice for this evening. With the classic Dynaco A-25's etc unless the cap is defective, such as is open, leave it alone. Some folks replace the caps with new ones and are happy. With the resistors unless you see one or more cracked or burnt up, which I've never seen, leave alone as well. Some folks replace the resistors and are happy. The cabinets fiberglass insulation was particularly fine material and without question should be left intact. There is much synthetic material which might do as good a job but without test equipment you will likely end up with less than you started with. The vent opening was covered with a particular piece of fiberglass which was determined by lab equipment. The switches were of good quality and very reliable. Wire was adequate for the job. Overall the Dynaco A-25 and family are well designed at a dollar compromise. No foam rot is a big plus issue. When a replacement driver is needed there was so many sold that there is a flood of used OEM drivers available. Vern
  2. Dynaco amp mods and tweeks

    Hi Joel The site referral is a site without an active forum. The repair was written by Kevin Boales for PC-28 circuit boards. I can print out the St-400, etc, mod for my use but I do not know how to just save it. This mod is for usually one dead channel and it covers replacing a common cause of the one dead channel. I do not feel it is ok for me to print out that file and re-scan it and post it here.
  3. Dynaco amp mods and tweeks

    I have a few mods or tweeks information on Dynaco's ST-150, ST-400, ST-410, ST-416 amps also series 80 amps and ST-120. If there is sufficient interest I will follow up here in the near future. If I remember correctly there was a phase 2 Dynaco ST-400, I have no information on why there was this added model designation. It may have been an internal doc. Please post here if you are interested in following up on these issues. Remember there is a serious risk of shock if you are not experienced. There was a TIP mod well known for the ST-120 but there was also a similar TIP mod for the 80 series. The mod for the ST150 - ST-416 amps is on Greg Dunn's web site. It was posted there around 2002. You can print out the article. A set of 8 pages has been deleted there that would have created a 600 watt mono amplifier. No explanation posted. Perhaps liability issue. Vern I do not have an email address yet.
  4. Should the AR-5 have been a 12" Speaker?

    Hi Frank It appears that you have all of the toy's and all in one room my friend. Vern
  5. Hi there Thank you for posting this information here. Vern
  6. AR Turntable Documents

    Hi there Thank you for posting this information here. Vern
  7. Dynaco A-25's & Subwoofer

    Hi there Just a small comment here. The original Dynaco A-25's were very well liked in their day. J. Gordon Holt of the original Stereophile Magazine fame went gaga over them in his first review. Very smooth and wide range, within their limits. I like them very much. Use caution with any bass boost, loudness controls or loud volume levels. You might download Dynacophil's "Dynaco Dynamax" paper from this site. It show's several options for multiple Dynaco speakers of the same brand and model. There is no reason the same cannot be used with most all 8 ohm speakers, at least to experiment with. For more bass, maybe if you have a friend with another pair of A-25's, try paralleling them together. Fusing them with a 3/4 or 1 amp fast blow fuse in an open style fuse-holder will help protect your investment at least. Just a thought. Vern
  8. HELP! Has anyone figured out KLH tweeters?

    Hi Kent I am certainly not an expert but the tweeter must have a totally enclosed metal frame so that the woofer back pressure does not pop out the tweeters cone material. I have seen some tweeters with holes stamped into the frames, but the correct version will not have any holes. The same with the mids. They had intentionally installed special sealed sub enclosures to prevent that type of accident. The satellite speakers with a single mid/fullrange driver would not have any issues in this regard. Vern
  9. Dynaco A-50 cabinet salvage

    Sorry for not posting photos. I took a lot of photos, but at too high a resolution to post here. Here it is 5 years later and I have still not posted them. There is photo editing software that I am trying to locate to allow me to post them. The photos of the work are too nice to not complete this article. The work that was done can be done to any walnut or other wood veneers. I may remove a woofer to photograph the inside of the enclosure and crossover network and even take some measurements. Originally I commented that the rear cabinets corners had the metal brackets for hanging on a wall and this wall not as Dynaco had advertised them, despite their light weight. Dynaco had several times advertised artists conceptions of their products and then altered the final product appearance, sometimes several times. Till next time. Vern
  10. KLH Twelve speaker info

    Hi Kent Thank you very much for your posting of photo. Vern
  11. KLH Twelve speaker info

    Hi there Is there a speaker review or schematic of this speaker system available?.
  12. Well, it's been a while, but one of my two amps died. My first thought, because I saw something glow red how in the case when I turned the unit on, was the unit suffered a cascade failure. AKA not cost effective to repair.

    Fall is here, my depression over the event has abated a bit and I decided to open the unit to see how bad the damage was before trashing. No burn marks, no scorched wires or melted or loose connections to be found. Checking further, both 5 amp fuses were blown in the right channel, the channel that failed.

    I decided to check the TO-3 transistors first, and found two that are a dead short between B-C-E. Each was part of a pair, it's matched transistor was good, er, acceptable given it's age.

    Checking further, I noticed whatever repair facility replaced 2 of the 4 NPN transistors in the channel, and used the wrong part number.

    The original part numbers are now obsolete (MJ15024 and MJ15025) but two substitutions are available. The better choices for the TO-3 NPN and PNP transistors is MJ21193G and MJ21196G. Mouses strongly recommended replacing all eight if going with these options. They have a slightly higher gain than the originals, supposedly better linearity and a high SOA.


    If this fixes the amp, this plus the new electrolytic caps should be a minor upgrade in performance and perhaps extend this old Heathkit AA-1800's life a few more decades.


  13. Improving The KLH Five - A New tweeter???

    Hi there Check out Ebuy for a used pair. The original tweeter was well regarded, not only in the Fives.
  14. KLH Twelve vs Five (drivers)--another piece of the puzzle

    Hi there Check your woofers cones for the black felt marked 25+/- or other numbers. This is the cone weight and depending how low the number was determined which model it was installed in. The opposite is also the the same.
  15. Dynaco A25 Vent Damping

    Hi there Put back the original piece of fiberglass.