Hello everybody
I would like to ask for help with the following. When I turn on the F6 power amp shortly (few seconds) after switching on the DCG3 preamp I noticed that this results in blown fuse in the F6. Waiting for few minutes before turning on the power amp does not show this behaviour. Is this likely because so far I have not installed a CL60 thermistor in the DCG3? None of the amps has a soft start built in. Any input would be much appreciated.
I would like to ask for help with the following. When I turn on the F6 power amp shortly (few seconds) after switching on the DCG3 preamp I noticed that this results in blown fuse in the F6. Waiting for few minutes before turning on the power amp does not show this behaviour. Is this likely because so far I have not installed a CL60 thermistor in the DCG3? None of the amps has a soft start built in. Any input would be much appreciated.
I used a PRB FRW9.7 main belt in the ONKYO. From few NOS left in a small USA store. For back-tension square section small belt I used one from Thakker Germany. I had the set from them but I replaced their main belt and kept it as a spare because the PRB worked smoother measuring better wow & flutter.
Also check these guys if you can find something that suits you: https://www.dynamtechgroup.com/tape-reel-belts.php
Also check these guys if you can find something that suits you: https://www.dynamtechgroup.com/tape-reel-belts.php
One thing is its safer to wait hear the relay click from DCG3 before turning on the amp. That takes 5-10 sec. To avoid pass a plop from the relay contacts. About having the CL60 installed or not I am not sure if related but maybe that could play a role too if its not about the standard dcg3 stabilization delay mentioned.
What kind of fuse does it blow in the F6? Rail fuse or primary fuse? Is it slow blow type? Maybe too closely fused for current rating?
Hmm... 1.25A primary fuse for a 300VA transformer seems small. Looks like 3.5A slow blow is recommended to withstand inrush current in 230V countries for such a transformer. See there in second page: https://solahevidutysales.com/pdf/transformers/Fusing.pdf
Do you still have the TDK tapes? I’d happily buy some from you?to buy a pre amp with a tape loop
I couldn't even give away unopen premium TDK cassette tapes 2 months ago after a major audio equipment housecleaning, my audiophile friends have all ditch their analog recorder.
Thanks very much Salas.
If I understand the F6 build guide correctly a 1.25 A (2.5A in 120V) slow blow fuse in 240V environment is used and a 300-400VA transformer is recommended for this project (https://www.diyaudio.com/community/threads/f6-illustrated-build-guide.277850/).
Total filter capacitance of the PSU is 2 x 88000uF.
I did not notice blown fuses when only the SBT was connected to the F6.
Maybe in combination with those TH limiters and 2 x 60000uF they manage to keep it that closely fused. Still, the international practice suggests 300% higher primary fuse for less than 2A nominal primary current single phase mains transformers. Nominal is VA divided by mains voltage. You could take a cautious step by trying 2A SLB primary fuse and see what happens. Since you use 22000 uF capacitor units its a heavier than the norm F6 PSU already.
Thanks very much Salas. That sounds reasonable. Definitely will try a 2A slow blow fuse and keep that in mind when ordering parts next time.
Good day Salas,
Re. DCG3, I have the following pots in my inventory: a 50 K blue Alps; a 50 K black Alps; a 100 K shielded TKD (2CP-2508-S). The TKD has the best sound as it was bought to replace an unshielded TKD 2500 years earlier. Can I use the 100k TKD by changing the value of R2 on the DCG3. I prefer the rounded sound of a 50 K pot as per previous posting.
Thank you very much for your time.
Re. DCG3, I have the following pots in my inventory: a 50 K blue Alps; a 50 K black Alps; a 100 K shielded TKD (2CP-2508-S). The TKD has the best sound as it was bought to replace an unshielded TKD 2500 years earlier. Can I use the 100k TKD by changing the value of R2 on the DCG3. I prefer the rounded sound of a 50 K pot as per previous posting.
Thank you very much for your time.
Thanks Salas, sorry I didn't made myself clear enough. I was thinking of using the 100k TKD because of better SQ, but was concern about that it is not the 20k to 50k range that you recommend all along. Based on your advise, would it be better if I put a 100k resister between the G pin and I pin to made it 50k impedance although I got a feeling that there is a price to pay by doing so.
The log curve is going to be affected if you will put that parallel resistor between wiper and ground. It will open up the volume more aggressively as you turn. Just try your 100k TKD as normally applied, that will not create a technical problem. By my calculation is it is simply going to restrict the response to 250kHZ -3dB worst case (when at mid value position). Which is not bad spec in general. It can go to 800kHz with 20k pot or to 400kHz with 50k pot. That's the difference.