What an absolutely incredible piece of work this UFSP is, I know, many before me here lament about its qualities but its not until you fire up your own and listen to it in your own system that you realise just how WOW it actually is.
I fired mine up this morning to get the burn-in under way, and over the five hours I can hear it opening up already.
A big thank you to Salas for sharing to all of us here, and then for the guidance through the mishaps along the way, where else in the world would you get such knowledgable and detailed directions, and in a very short time.
A big thank you to Teabag too, for sourcing, matching, assembling and shipping these kits to us, and also producing assembly guides, not an easy task.
I didn't intend the layout below but when I ordered the case from Italy on their website I selected L x W instead of W x L and ended up with this shaped box, so I had to use it and find a way to make it work, this is how it turned out.
Before the Ultra is a Technics SL1200 that I purchased 42 years ago, after the Ultra is the Fantastic Salas DCG3 built in 2018, then a Hiraga Le Monstre with original Hitachi outputs (like night and day comparing to Onsemi's) and this feeds into a pair of 1971 Altec 604-8G studio monitors in 9cu ft cabinets.
Still some tidying up to be done before the lid goes on but I'm walking around all day with a smile listening to it, just incredible. Somebody here (I think 6L6) said if you're thinking of building one, just do it, you won't be sorry! So true!
Again Thank you Salas and Thank you Teabag.
I fired mine up this morning to get the burn-in under way, and over the five hours I can hear it opening up already.
A big thank you to Salas for sharing to all of us here, and then for the guidance through the mishaps along the way, where else in the world would you get such knowledgable and detailed directions, and in a very short time.
A big thank you to Teabag too, for sourcing, matching, assembling and shipping these kits to us, and also producing assembly guides, not an easy task.
I didn't intend the layout below but when I ordered the case from Italy on their website I selected L x W instead of W x L and ended up with this shaped box, so I had to use it and find a way to make it work, this is how it turned out.
Before the Ultra is a Technics SL1200 that I purchased 42 years ago, after the Ultra is the Fantastic Salas DCG3 built in 2018, then a Hiraga Le Monstre with original Hitachi outputs (like night and day comparing to Onsemi's) and this feeds into a pair of 1971 Altec 604-8G studio monitors in 9cu ft cabinets.
Still some tidying up to be done before the lid goes on but I'm walking around all day with a smile listening to it, just incredible. Somebody here (I think 6L6) said if you're thinking of building one, just do it, you won't be sorry! So true!
Again Thank you Salas and Thank you Teabag.
Nice system and interesting vintage speakers the Altec 604-8G studio monitors. What phono cartridge you use on the Technics?
How you decided to tackle the 3 Leds different mA due to in one shunt reg J1 reversal mishap? Another J1 or a smaller value R4?
Thanks Salas, I got a new DL103R for the Technics so it was burning in too long with the Ultra. I do want to get a Hana ML soon.
I piggybacked another 270r onto the R4 and it made the LED's brighter but didn't affect the V at the centre leg of J1, so I removed it again and decided to try out the amp with 33.9 on that channel and 34 on the other, and it all worked very well.
I had the system on continuously yesterday for 14 hours and again this morning for 4, and the channel with the issue stopped working. The Power side 3 LEDs are off but the Audio 4 LEDs are on. I checked the base of J1 and no power on any legs. The V out of the Power is 43.3, the good channel is 34.0.
I have some replacement J1's on the way from Tea, and have new LEDS's here, so hope nothing else is damaged.
I want to remove the board and disconnect the power link into the Audio side before doing any tests on it. I will remove the J1, and test the LED's in circuit, is there any other tests I can do? Sorry to be a nuisance with this Salas!
The 103R has a likeable tone and goes along well with vintage speakers too. The Hana ML has more resolution but still musical.
J1 most possibly got compromised during your original mishap and finally gave up the ghost.
No further tests to do until with a new J1. When replaced (along with new LEDs) test for proper R1 voltage drop and regulator output adjustment range. Before reconnecting the power link to the audio board.
*Pay attention to the LEDs correct orientation when replacing.
J1 most possibly got compromised during your original mishap and finally gave up the ghost.
No further tests to do until with a new J1. When replaced (along with new LEDs) test for proper R1 voltage drop and regulator output adjustment range. Before reconnecting the power link to the audio board.
*Pay attention to the LEDs correct orientation when replacing.
I tried four 5102s in this tester and I saw better mA than you but nothing near Idss as it runs the testing. I also saw higher Vgs than you saw. Hmm... Maybe you got a low Idss but still useful Jfet. Try the old Leds too.
I metered each LED on board and they have correct fv 1.650 and each one glows faintly when testing, I think the three are okay.
I will wait for new J1 and test it before fitting, and then verify each voltage against the good channel when fitted.
Will keep you advised, and Thank you.
I will wait for new J1 and test it before fitting, and then verify each voltage against the good channel when fitted.
Will keep you advised, and Thank you.
So some good and bad new, I pulled all transistors from power side to test out of circuit, one 560 was dead, refitted all along with new 560, powered up LEDs on and full voltage range 28 to 38, set to 34, powered down and connected audio side, all LED's on but no volts at TP, turned pot end to end, nothing.I have S9 on, I have 30v on outside of the 1.2k resistor but no volts on the switch side, S10, 11 & 12 are off and have voltage from their R14, 15 & 16 but goes to zero if they are turned on.
The other channel is perfect so convenient for comparing voltages at various points.
I removed Q1, 2 & 3 to test. Q3 is good and healthy but Q1 & 2 I think are in trouble. See the attach image, not even showing up as a Jfet and both are exactly the same.
Fix one problem and create a new one!
The other channel is perfect so convenient for comparing voltages at various points.
I removed Q1, 2 & 3 to test. Q3 is good and healthy but Q1 & 2 I think are in trouble. See the attach image, not even showing up as a Jfet and both are exactly the same.
Fix one problem and create a new one!
The rail went high when the PSU was out and probably hit something(s) in the audio board.
You can recheck the K369s with a meter for RDS. In Ohms mode you measure the JFET from drain to source with the gate touching source i.e. resistance between pin 1 and 2+3. Looking for low value 20-30Ω for this high transconductance type if healthy.
How's Q7 testing?
You can recheck the K369s with a meter for RDS. In Ohms mode you measure the JFET from drain to source with the gate touching source i.e. resistance between pin 1 and 2+3. Looking for low value 20-30Ω for this high transconductance type if healthy.
How's Q7 testing?
Reassembled to test voltages, first test was the TP, and it had 4v. I don't know how or why. I didn't check any other voltages. Left it for an hour to warm and stabilise, plugged into the system and its perfect. I guess the worrying part is not knowing what was wrong but that's another adventure for another day!
I must say I learned much more about this amp through troubleshooting compared with a straight assembly, lid on and into a system, so Thank you again Salas
I must say I learned much more about this amp through troubleshooting compared with a straight assembly, lid on and into a system, so Thank you again Salas
RDS is 1/Gm roughly proportional and inverse to IDSS. Only 0.2Ω difference also hints to very good IDSS matching for Q1 Q2.