Questions about the Frigate®

[comelsys]

I finished the assembly kit.
But I have a couple of questions.
Firstly, is not very clear why the heater power is provided by a 12 AC? Whether it was better powered it 6 AC, and the bridge would be 8-8.5 DC, and then reduced to 6.3 DC? Radiators are very hot, and the transformer is warm. I measured the filament voltage of 6.7 and 6.9 DC. Not too high voltage?
And secondly enclose the file where the resulting measurements marked on both 6N30P. In Scheme 250 DC power , but in fact 300DC.
Otherwise, everything turned out very well and I am very pleased with the amplifier.

[Augustica.com]

1. The reasons for using filament transformers with 12 AC output is as follows. The filament transformers' power (in this case 30W which is calculated as W = V x I) has to be such so it could supply a clean AC voltage to Trident and subsequently supply clean DC voltage to Frigate. The current that flows through each filament bus of Trident and Frigate is 1.5 A. This is a substantial current. Selecting transformers' AC voltage lower than 12 AC would result in insufficient current produced by the transformers and insufficient DC voltage produced by Trident. Since power is calculated as W = V x I, to sustain the current required by Frigate, the voltage would drop to the lever below 6.3 VDC and you would hear ripple in your headphones. Also, for LD1084 to give out at least 6.3VDC, they would need to receive at least 9.0VDC in. As you can see, taking in consideration all the above, the minimum output AC voltage for the filament transformer should be 12 VAC.

You measured filament DC voltage without any load connected to the Trident. Once you connect Frigate to the Trident, the voltage will drop to 6.3 - 6.6VDC.

2. The heat sinks of all three voltage regulators have to be hot. That is the reason they are placed on heat sinks. The current that floes through filament voltage regulators is 1.5A and the current that flows though the B+ voltage regulator is 0.1A. These are substantial currents and therefore the regulators become hot. Both transformers, filament and B+, should be warm with temperature staying steady at about +35 C.

3. Some customers buy Frigate without power supply Trident and they use their own power supplies. This is not recommended but this is their choice. Since we do not know what voltage their power supplies would produce, we have shown on the Frigate's schematic that the B+ voltage has to be +250 VDC. The Trident power supply provides about +280 VDC without a load and +250 VDC with a load.

Please post photos of your Frigate and Trident assembly.

[comelsys]

1. Not quite agree with your point of view. Yes, a couple of 6N30P and 6922 consumes 1.5A at a voltage of 6.3DC. If you use a transformer with 9AC and 25-30VA, for example 182K9 or 182M9, these transformers provide the necessary current and will be less load LD1084V and it will not be so hard to warm up.

Voltage regulator after 6.7DC and 6.9DC I measured is connected Frigate with tubes.

2. I ask you to explain to me the measured voltage to the 6N30P. Voltages are very different of channels. Not too high voltage?

Photos can not do it until , after 10 days, be sure to send.

[Augustica.com]

1. We all have opinions. The difference between your opinion and mine is in the fact that my opinion is based on experience. I experimented with 182K9 and 182M9 and they did not produce clean DC voltage and did not produce enough power. If you feel strongly about this issue, you may purchase those transformers and find out that I am correct. Further, voltage does not produce heat, it is current that produces heat. Changing voltage to 9VAC from 12VAC will result in a "dirty" DC filament voltage and similarly hot regulators IC2 and IC3 which will be only marginally operational due to insufficient DC voltage applied to them.

2. Your left channel voltages are exactly as designed. Your right channel voltages should be the same. You might have misplaced some resistors in the right channel and it is the most likely reason why the voltages are not the same. Check out that all resistors of the left channel are mirrored by the resistors in the right channel. Again, your left channel voltages are as they should be and these voltages are your reference for the right channel.

3. 6.7VDC for filament is within limits, but 6.9VDC is a bit high. You need to adjust resistors R8 and R9 which are responsible for the voltages produced by the voltage regulator IC3. Let me know if you need assistance in this regard.

[comelsys]

1. Thanks for the elucidation. I'll leave you recommended 182L12.

2. Apparently the problem with tubes 6N30P. I rearrange them and voltage are reversed.
All other parts I checked, all matches scheme.

3. Help, please. What should be done with resistors R8 and R9?

[Augustica.com]

1. In addition to the factors mentioned previously, you also have to appreciate that Frigate (and Corvette for this matter) are designed with a possibility to roll in different tubes. If you roll in 6P1P instead of 6922 your total current per each filament bus will increase from 1.5 A to 2.0 A. The transformers you are proposing to use will not operate at all with 6H1P.

2. Are you certain that swapping the 6H30Pi tubes moves the problem to the left channel? The reason I am asking is that before the kit was shipped both 6H30Pi tubes were installed in the amplifier in the shop and voltages were measured as designed. If you are certain, I will mail to you two 6H30Pi as a replacement.

3. If you look at the datasheet for LD1084, you will see that the output voltage produced by the LD1084 is determined by the formula:

Vout = 1.25 (1 + R8/R9)

Where
R8 - 511 Ohm
R9 = 110 Ohm
1.25 is reference voltage

You need to increase resistance of R8 from 110 Ohm to 124 Ohm and it should bring your filament voltage to about 6.5 VDC.

I will send you a couple of 124 Ohm resistors with the tubes.

Any other questions?

[comelsys]

2. Yes, sure! Voltage at the tubes 6922 - ideal. And 6N30P such as illustrated. If change 6N30P, voltage change after the tubes.

3. I read the datasheet for LD1084. First thought: 1.25 * (1 + (511/110)) = 7.05.
Thought it would be a reduction of tension, checked all the items - everything was installed correctly.

I would be very grateful if you could send me a pair of 6N30P and resistors 124 Ohm.

And I, as promised, send photos of Frigate separately and photos of Frigate mounted in the enclosure.

P.S.
I really liked your approach to customers, as well as the quality of components and high-quality printed circuit boards.
I hope I will still order from you for completing my other projects.

[Augustica.com]

2. Sending a pair of 6H30Pi is not a problem and it is an easy part. The difficult part is to nail the problem. I want to make sure that the problem is indeed in the tube and not in the diodes D4, D5, D6 and resistors R29 and R30. Your voltages suggest that the diodes may not operate and therefore do not provide the required bias to the cathode and grid of the tube in the right channel. Could you please measure and post voltages on anodes of each D4, D5, D6 from the GND up and also voltages on R29 and R30.

3. Each transformer and voltage regulator is different and yours provide slightly higher DC than designed. The Trident in the shop has R8=511 Ohm and R9=110 Ohm and the resulting voltage is 6.5 VDC for each bus with Frigate connected to Trident.

Lets confirm that the diodes and resistors work and have voltages as designed and that the problem is indeed in the tube.

[comelsys]

Ok
Unfortunately, I am now on a business trip. I'll be home in 10 days. I will measure all the required voltages and send photos.

[comelsys]

So, as promised, I post photos of my Frigate. On some photos showing the measurement results.