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Eico Hf-81 Integrated Amplifier
Eico Hf-81 Integrated Amplifier
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Old 7th February 2011, 05:56 AM   #1
orly40 is offline orly40  United States
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Smile Eico Hf-81 Integrated Amplifier

Hello everyone i am new at this i just purchased a Eico HF-81 this amp sounds really good no problems other than a little hum .My question is i opened the top today to clean the dust inside and noticed that while the amp is operating some of the tubes they are not lit for example v5 and v6 and the others have a metal enclosure v1,v2,v3 and v4 i dont see a glow either is this normal? V7 thru v12 all glow .i am using the aux A imput .
Thanks in advance Orlando
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Old 7th February 2011, 11:41 AM   #2
dcgillespie is offline dcgillespie  United States
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Location: Ball Ground, GA
The tubes you identified are the smaller tubes in the amplifier. These small signal tubes have much smaller heaters inside them, so that their glow will often not be as apparent as that of the power and rectifier tubes, which are the taller ones. If the tubes you are concerned with were not heating at all, you would get no sound from the amplifier.

Since you indicate you are having to clean the unit, cleaning the tube sockets with a good electronic cleaning agent will make sure that the tube pins are all making good contact in their sockets. This can be an issue in older equipment if it has not been thoroughly gone through, which would be very advisable to do if you are looking to achieve long term dependability.

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Old 7th February 2011, 11:46 AM   #3
mastodon is offline mastodon  Netherlands
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V5 should look the same as V4, V9 and V10. If it doesn't work, channel 1 will sound awfully distorted. V6 should look the same as V1, V3 and V8. If it doesn't glow at all, there should be no sound coming from channel 2.
/edit: ignore the above; I referred to the tube numbers in the schematic, and they don't match with the layout.

The metal enclosures are there to prevent interference from external sources and the power transformer. They should be installed on V1, V2, V3 and V4, which seems to be correct in your amp. You can remove the cover to check the tubes, but if your amp functions properly, there's no need to (except for curiosity, of course).

Check V5 and V6 again; in some tubes, it's hard to see the glow.
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Old 7th February 2011, 01:44 PM   #4
orly40 is offline orly40  United States
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Thank you so much so far nothing to worry about !!
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