Bottlehead Forum
Bottlehead Kits => Eros Phono => Topic started by: arveedub on January 09, 2010, 08:46:29 AM
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I completed my Eros phono kit, but some of my resistance measurements are off. Comparing the schematic, supplied parts & manual I found that they don't seem to agree. Here are the issues:
- T9 calls for 39K to ground, yet the schematic calls for a 47K resistor (which is exactly what was supplied with the kit). My measurements were 46K.
T4 calls for 60K to ground, yet the schematic calls for a 75K resistor (once again supplied with the kit). My measurements were 75K.
T2 calls for 71K to ground, yet the schematic has 75K & 10.5K resistors (supplied with kit). My measurements were 85.7K.
Perhaps the measurements for the tape version made their way into the phono version manual?
Once this is sorted out, maybe I can get some help on why I have 158V on OA.
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Looking at the schematic, I can see that with some meters, if the resistances are measured with the right polarity, there can be some current flowing through the C4S output transistor back to ground through the C4S bias resistor (120K or 220K) which would produce the results in the manual. With the meter leads in the other polarity, I would expect your measurements - these would seem to be the more appropriate ones, and the manual should probably be corrected.
If OB is not more than 100v, then 158 on OA is fine.
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Thanks, Paul
The amp sounded too good to be wrong, but I just wanted to make sure.
You really cooked up a special little amp with the Eros. Congratulations are very much in order.