Tweet
Hi guys,
I'm a mad Echoplex collector, I have 16 of them. I know, I'm insane
I've been able to fix any problem with them so far except my latest EP-3 which I just cannot get to do runaway oscillations. The echo sounds great but its really weak and doesn't sustain for long, its also much lower in volume than my other EP-3's.
I've performed the following surgery so far;
* Tried a variety of different tapes, old and brand new
* Demagnetized and cleaned tape heads
* Installed new drive belt
* Replaced filter capacitors and zener diode
* Replaced capacitors on on bias oscillator board
* Realigned heads using oscilloscope as per the service manual
* Adjusted echo sustain trimcap
* Adjusted bias oscillator trimpot
* Changed Q5 (TIS58) transistor
* Changed Q4 (TIS98) transistor
* Checked voltages of transistors and other components, all OK.
This would usually get an Echoplex working perfectly but nothing I've done so far has made any major difference. I'm at the point now where I'm thinking it could be an issue with the tape heads even though they are the cleanest looking heads in my collection. So after all that my question is, how can I test the tape heads to make sure they're up to spec?
Thanks in advance for any help, tearing my hair out!
jbgron
I'm a mad Echoplex collector, I have 16 of them. I know, I'm insane
I've been able to fix any problem with them so far except my latest EP-3 which I just cannot get to do runaway oscillations. The echo sounds great but its really weak and doesn't sustain for long, its also much lower in volume than my other EP-3's.I've performed the following surgery so far;
* Tried a variety of different tapes, old and brand new
* Demagnetized and cleaned tape heads
* Installed new drive belt
* Replaced filter capacitors and zener diode
* Replaced capacitors on on bias oscillator board
* Realigned heads using oscilloscope as per the service manual
* Adjusted echo sustain trimcap
* Adjusted bias oscillator trimpot
* Changed Q5 (TIS58) transistor
* Changed Q4 (TIS98) transistor
* Checked voltages of transistors and other components, all OK.
This would usually get an Echoplex working perfectly but nothing I've done so far has made any major difference. I'm at the point now where I'm thinking it could be an issue with the tape heads even though they are the cleanest looking heads in my collection. So after all that my question is, how can I test the tape heads to make sure they're up to spec?
Thanks in advance for any help, tearing my hair out!
jbgron
Comment