I built myself a PAT-4, ST-120 and FM5 back in 1970 when I was in high school. My friends enjoyed these so much I built kits for them as well. As such over the years I have had a lot of experience servicing these and keeping them going. From what I see on your ST-80 you might want to perform the "TIP mod". The PAT5's were designed an always live power supply to eliminate the turn-on thump. The front panel on/off switch only controlled the back panel outlets. EPL was "External Processor Loop" for an equalizer. On the PAT-4 phono inputs the High is High Level and the Low is Low Level (some magnetic cartridges had too much output for the Low input). The power supply is, of course, DC and the rectifiers are on the terminal strip next to the accessory outlets.
Not sure what the TIP mod is. I'd like to get the amp working stock before trying any mods. I do have parts kits from updatemydynaco website for the PAT4 (incl. new PS board) and ST80.. Just haven't got around to implementing the repairs yet
@@bblimediamostlyspeakers The TIP mod uses TIP31 and TIP32 transistors to replace the TO-5 transistors for the drivers. This was implemented to improve the reliability.
I just restored a PAT-5. If there’s AC on the chassis, that’s a wiring or death cap fault. Replaced e-caps, the transistor that is used to regulate the +42V (?) supply, and the power resistors in the supply with much stouter finned ones. Disassembled, cleaned, and re-lubed pots; balance and volume were hard to turn. That power switch in the front only affects the outlets in the back; if the preamp is plugged into a live socket, it’s on. As for that amp, I don’t think that power resistor is charred - I think the amp lived in smoke and you’re seeing a convection stain. Replace it with a finned one anyway.
When replacing the AC line capacitors, make sure you order X type if across the line and Y type of connected to ground. These are designed to fail open with age. They aren't that expensive although a bit more than cheap ceramics.
Dynaco was a mixed bag because often longevity wasn't a strong suit. They had some huge successes however. The ST-70 tube amplifier was their absolute iconic product. Not only was it an amazing performer, but the value was off the charts - especially if you were inclined to build it yourself. Because of its basic, but robustly, sound design it has been not only revived several times, but widely emulated. The Dynaco A-25 speaker was another iconic product with amazing value all over it. David Hafler's matrix quad system leveraged ambiance brilliantly only requiring two more speakers without additional amplification. Even Dynaco's solid state designs were pretty good values, but time hasn't been as kind to them. For instance, I had the ST-400 amp and it was good for about three years then it became one problem after another. I actually chunked it which I am ashamed of doing at this later date. I didn't give up on Mr. Hafler and later bought three of his amplifiers under the Hafler name. The sound was always the first thing, Dynaco and Hafler got that right.
I really like the Hafler amplifiers, have a trio of Hafler P500s, one is powering my subs. Very tight bass, and great sounding, but need repairs. Also don't need quite that much power all the time so got the ST-80 to try to rebuild. It looks like an easy place to start and I'm not into tubes yet. I'm really curious how good it will be as I've never heard the Dynaco stuff before. Hopefully it's not too expensive to fix :)
All the first generation 400 watt amplifiers of that era were highly prone to failure. Dynaco, Phase Linear, Marantz. It was the power transistor technology of the time. Those designs pushed them to the limit. A 400 watt amplifier is no big deal today and they are highly stable and reliable.
I built a ST-120 and PAT-4 in 1968 while stationed at Ft Benning and used them through the 70's. They were pretty robust and fairly priced but I recall the phono section being a little hissy.
![[[OFFICIAL MV]] เอิ้นขวัญให้อ้าย- อ๊ะอาย สกุณาพร | ค่ายเพลงเป็นหนึ่ง](http://i.ytimg.com/vi/83x6L3X3qh0/mqdefault.jpg)
I built myself a PAT-4, ST-120 and FM5 back in 1970 when I was in high school. My friends enjoyed these so much I built kits for them as well. As such over the years I have had a lot of experience servicing these and keeping them going. From what I see on your ST-80 you might want to perform the "TIP mod". The PAT5's were designed an always live power supply to eliminate the turn-on thump. The front panel on/off switch only controlled the back panel outlets. EPL was "External Processor Loop" for an equalizer. On the PAT-4 phono inputs the High is High Level and the Low is Low Level (some magnetic cartridges had too much output for the Low input). The power supply is, of course, DC and the rectifiers are on the terminal strip next to the accessory outlets.
Not sure what the TIP mod is. I'd like to get the amp working stock before trying any mods. I do have parts kits from updatemydynaco website for the PAT4 (incl. new PS board) and ST80.. Just haven't got around to implementing the repairs yet
@@bblimediamostlyspeakers The TIP mod uses TIP31 and TIP32 transistors to replace the TO-5 transistors for the drivers. This was implemented to improve the reliability.
The older the amplifier is, the cooler looking 😊
Agreed! Same for certain speakers.
I just restored a PAT-5. If there’s AC on the chassis, that’s a wiring or death cap fault. Replaced e-caps, the transistor that is used to regulate the +42V (?) supply, and the power resistors in the supply with much stouter finned ones. Disassembled, cleaned, and re-lubed pots; balance and volume were hard to turn. That power switch in the front only affects the outlets in the back; if the preamp is plugged into a live socket, it’s on.
As for that amp, I don’t think that power resistor is charred - I think the amp lived in smoke and you’re seeing a convection stain. Replace it with a finned one anyway.
When replacing the AC line capacitors, make sure you order X type if across the line and Y type of connected to ground. These are designed to fail open with age. They aren't that expensive although a bit more than cheap ceramics.
Dynaco was a mixed bag because often longevity wasn't a strong suit. They had some huge successes however. The ST-70 tube amplifier was their absolute iconic product. Not only was it an amazing performer, but the value was off the charts - especially if you were inclined to build it yourself. Because of its basic, but robustly, sound design it has been not only revived several times, but widely emulated. The Dynaco A-25 speaker was another iconic product with amazing value all over it. David Hafler's matrix quad system leveraged ambiance brilliantly only requiring two more speakers without additional amplification. Even Dynaco's solid state designs were pretty good values, but time hasn't been as kind to them. For instance, I had the ST-400 amp and it was good for about three years then it became one problem after another. I actually chunked it which I am ashamed of doing at this later date. I didn't give up on Mr. Hafler and later bought three of his amplifiers under the Hafler name. The sound was always the first thing, Dynaco and Hafler got that right.
I really like the Hafler amplifiers, have a trio of Hafler P500s, one is powering my subs. Very tight bass, and great sounding, but need repairs. Also don't need quite that much power all the time so got the ST-80 to try to rebuild. It looks like an easy place to start and I'm not into tubes yet. I'm really curious how good it will be as I've never heard the Dynaco stuff before. Hopefully it's not too expensive to fix :)
All the first generation 400 watt amplifiers of that era were highly prone to failure. Dynaco, Phase Linear, Marantz. It was the power transistor technology of the time. Those designs pushed them to the limit. A 400 watt amplifier is no big deal today and they are highly stable and reliable.
EPL = External Processor Loop. One might use a Dynaco quad adapter (an early 4-channel surround system) or an equalizer.
Or a DBX dynamics processor. Those were big in that era.
I built a ST-120 and PAT-4 in 1968 while stationed at Ft Benning and used them through the 70's. They were pretty robust and fairly priced but I recall the phono section being a little hissy.
Thanks for watching.
It's the Dynaco TUBE amps that were really good, not the SS.
I know that, but I have these and the goal isn't for the best sounding, I'm set on fixing these so they work again.