Avalon 747 technical schematic

[pierre245]

Without load

Did you find the 6 V and 12 V as well as the bipolar 32 V?

Without load I get
- 6.3
-12.1
- 35/-35
And the other B+, 100 volts.

I have 35 not 32 .... Is it a problème ? Thanks

 

[pucho812]

Without load

Without load I get
- 6.3
-12.1
- 35/-35
And the other B+, 100 volts.

I have 35 not 32 .... Is it a problème ? Thanks

Without load, no that’s within spec

 

[pierre245]

Yesterday, I check the 250V caps. Guess what ?? Two Of them are so dry, they collapse only slowly when manipulate them. Its the 47 uf and the 100 uf. I change that 47 uf, now line is on 125 V... Waiting for others caps. I order it and received it today. I will finish recap tonight .. Hope that Can help the 747 to boot on correctly...

 

[pierre245]

Everything’s seems OK NOW ! PSU OK ! Compressor runs… Does it have some audio process (bias, calibrating) to do for optimize the gear ? I remember have some issue with some compressor who needs only some ajustements. Is there a process to do ? Thanks

 

[pucho812]

Everything’s seems OK NOW ! PSU OK ! Compressor runs… Does it have some audio process (bias, calibrating) to do for optimize the gear ? I remember have some issue with some compressor who needs only some ajustements. Is there a process to do ? Thanks

So your compressor is working?
This is good news.
Do you need calibration instructions? I have those.

 

[pierre245]

So your compressor is working?
This is good news.
Do you need calibration instructions? I have those.

Yeah ! 747 works ok now .... 180 line was off : I change only 2caps , 47uf and 1000uf on 250V. Yes I need these instructions for calibrage. If you have something it could help a lot .... Thanks Peter

 

[pucho812]

Here you go.
Any reference to AP is an audio precision machine. You can easily achieve results without an AP for calibration purposes, but you will not get the fancy noise floor and THD measurements. To work without an AP, you need a tone generator and a way to measure the output level. We are also starting at step 15 as steps 1 -14 consist of checking the PSU which you have already done, checking cosmetic things and other details not needed.


15. Connect Ap to both channels in and out and set AP to generate 1K @0dBu
16. Check level with Ap.input and output at center detent no eq no compression
17. Level should be even on both sides @ 0dBu.
18. Press high gain in
19. AP should read +10dBu
20. Press tsp in
21. AP should increase.2dB
22. Turn off high gain and TSP
23. Turn Output Pot full right
24. Ap should read +5dBu
25. Turn Output pot far left
26. Ap should read -27dBu +/-1dBu
27. Turn output pot to 9 o'clock position
28. AP should read .5dBu difference between channels
29. Turn output to center detent
30. Turn input pot to far right
31. AP should read 8dBu
32. Turn Input pot far left
33. AP should read -21dBu
34. Turn input pot to center detent
35. Adjust vr2 on Main Board to adjust channel 1 level to 0dBu as reflected on AP
36. Adjust vr3 on Main board to adjust Chanel 2 level to 0dBu as reflected on AP
37. Adjust VU meter to 0VU by turning trimpot accessed through the faceplate
38. Change level out of AP and watch the LED metering to make sure both channel track
together To adjust this metering at all Adjust vr4 on main board for Ch 1 and vr5 for CH2.
39. Set AP back to generate 1K @ 0dBu
40. Press compressor IN
41. Turn Compressor knob far left
42. Turn Make up gain knob far right
43. AP should read 10.45dBu
44. Press TSP IN
45. AP Should jump 1.3dB
46. Turn off TSP
47. Turn Make up Gain Far left
48. Turn Compressor pot far right

Avalon 747 Test Procedure By Joe Vezzetti

49. Turn Threshold far Left
50. Turn Attack and Release pots to fast
51. Adjust VR4 on card 5600-7474 so that ch1 is -10.10 on AP
52. Adjust VR6 on card 5600-7474 so that ch4 is -10.10 on AP
53. Adjust VR2 on card 5600-7474 So that the VU meter shows -10VU
54. Turn Compression pot to 10 O’clock Position
55. Adjust VR5 on card 5600-7474 so that ch1 is -3.10 on AP
56. Adjust VR6 on card 5600-7474 so that ch2 is -3.10 on AP
57. Adjust VR3 on card 5600-7474 So that the VU meter shows -3VU
58. Turn Compressor pot far right
59. Observe measurement
60. Repeat steps 51 - 57 until both channels match
61. Turn Compression pot far left and slowly increase it till AP reads -.4dBu
62. Adjust vr1 on Opto Card So that the Blue GR LED starts Blinking
63. Turn Compression pot far right
64. Monitor Noise with AP
65. AP Should show -88dBu noise floor
66. Press TSU in again
67. AP should show -88dBu Noise Floor
68. Press EQ IN
69. AP Should Show around -80dBu
70. Press EQ ou
71. AP Should Show -88dBu again
72. Connect 747 Ch 1 to FFT for following adjustments/measurement
73. Set FFT to read 2dB increments
74. Press EQ in
75. Plus up and Down on all eq sliders and watch that they go to correct levels.
Variable amplitude LF +/-24dB 15Hz shelf response
Variable amplitude MF1 +/-8dB 125Hz selected Q response
Variable amplitude MF2 +/-4dB 500Hz selected Q response
Variable amplitude MF3 +/-4dB 2kHz selected Q response
Variable amplitude MF4 +/-10dB 5kHz shelf response
Variable amplitude HF +/-20dB 32kHz shelf response
76. Push Compressor IN
77. Turn Compressor pot far right
78. Press SC-Listen IN
79. Turn Both sidechain threshold pots far left
80. Turn HF sidechain frequency Pot far right
81. Turn LF sidechain frequency pot to 12 o’clock
82. FFT should show two lumps on the line
83. Press sidechain IN
84. FFT level should drop to the bottom of the screen
85. Press sidechain Listen out
86. Repeats FFT measurements for ch 2