# After 37 years my 4.6 phono stage needs help **URL:** \ **Category:** Preamplifiers\ **Created:** [November 27, 2024, 7:45pm UTC](https://forum.psaudio.com/t/after-37-years-my-4-6-phono-stage-needs-help/40092 "2024-11-27T19:45:50Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Winslow](https://avatars.discourse-cdn.com/v4/letter/w/4af34b/32.png) [@Winslow](https://forum.psaudio.com/u/Winslow)\ **Post date:** [November 27, 2024, 7:45pm UTC](https://forum.psaudio.com/t/after-37-years-my-4-6-phono-stage-needs-help/40092/1 "2024-11-27T19:45:50Z")
Hi all, This is my first post. I’ve owned my PS Audio 4.6 pre amp since the late 80s. Aside from some scratchy pots over the years it’s been trouble-free (no cap job or any other interventions) and of course the phono stage sounds great. Til now, that is. Today I noticed some hash/distortion on the left channel. The ol’ scientific revealed that the left phono input is compromised. This is true for Straightwire, High Gain, or Mono modes. Short of full cap job, any suggestions on where to start just to get it up and running? Other inputs are fine. Thanks! Happy Thanksgiving! - Winslow ---
**Author:** ![Paul](https://sea1.discourse-cdn.com/flex015/user_avatar/forum.psaudio.com/paul/32/6_2.png) [@Paul](https://forum.psaudio.com/u/Paul)\ **Post date:** [November 27, 2024, 11:07pm UTC](https://forum.psaudio.com/t/after-37-years-my-4-6-phono-stage-needs-help/40092/2 "2024-11-27T23:07:45Z")
That’s an oldie buit goodie and I would guess caps are not happy. Start with replacing all the power supply caps and see if it doesn’t help. All in you’re probably looking at less than $20. ---
**Author:** ![Winslow](https://avatars.discourse-cdn.com/v4/letter/w/4af34b/32.png) [@Winslow](https://forum.psaudio.com/u/Winslow)\ **Post date:** [November 29, 2024, 4:40pm UTC](https://forum.psaudio.com/t/after-37-years-my-4-6-phono-stage-needs-help/40092/3 "2024-11-29T16:40:24Z")
Thanks Paul. The other inputs work fine. Can bad caps in the power supply only affect the phono stage but not the others? - Blake ---
**Author:** ![Paul](https://sea1.discourse-cdn.com/flex015/user_avatar/forum.psaudio.com/paul/32/6_2.png) [@Paul](https://forum.psaudio.com/u/Paul)\ **Post date:** [November 30, 2024, 1:15pm UTC](https://forum.psaudio.com/t/after-37-years-my-4-6-phono-stage-needs-help/40092/4 "2024-11-30T13:15:51Z")
No. So that’s out. Maybe look at the coupling caps on that (both actually) input. Those are cheap and easy to replace. ---
**Author:** ![weedeewop](https://sea1.discourse-cdn.com/flex015/user_avatar/forum.psaudio.com/weedeewop/32/190064_2.png) [@weedeewop](https://forum.psaudio.com/u/weedeewop)\ **Post date:** [December 1, 2024, 5:36pm UTC](https://forum.psaudio.com/t/after-37-years-my-4-6-phono-stage-needs-help/40092/5 "2024-12-01T17:36:40Z")
Considering its age a complete electrolytic recap seems to be worthwhile. A schematic from PS Audio may be helpful in identifying the actual caps. ---
**Author:** ![Subidiom](https://avatars.discourse-cdn.com/v4/letter/s/6de8d8/32.png) [@Subidiom](https://forum.psaudio.com/u/Subidiom)\ **Post date:** [November 11, 2025, 10:59pm UTC](https://forum.psaudio.com/t/after-37-years-my-4-6-phono-stage-needs-help/40092/6 "2025-11-11T22:59:44Z")
Resurrecting this thread since I just finished my 4.6 restoration. I also had distortion in the left channel of the phono stage. After replacing all of the electrolytics on my unit, the issue was still there, so my next step was to replace the BJTs. I found a supply of NOS Motorola MPS 8099/8599 for a dollar each, so I went ahead and refreshed them all. I found 4 bad transistors, including one in the phono stage left channel with an hFE of “2” - this was totally worth doing! I have pretty accurate schematics of the amplifier gain stages and am happy to share my experience restoring this classic pre. It’s totally worth the effort! ---
**Author:** ![weedeewop](https://sea1.discourse-cdn.com/flex015/user_avatar/forum.psaudio.com/weedeewop/32/190064_2.png) [@weedeewop](https://forum.psaudio.com/u/weedeewop)\ **Post date:** [November 12, 2025, 2:40am UTC](https://forum.psaudio.com/t/after-37-years-my-4-6-phono-stage-needs-help/40092/7 "2025-11-12T02:40:25Z")
Rectifiers next? ---
**Author:** ![Subidiom](https://avatars.discourse-cdn.com/v4/letter/s/6de8d8/32.png) [@Subidiom](https://forum.psaudio.com/u/Subidiom)\ **Post date:** [November 12, 2025, 2:52am UTC](https://forum.psaudio.com/t/after-37-years-my-4-6-phono-stage-needs-help/40092/8 "2025-11-12T02:52:13Z")
Uh, if you’re already in the patient as the saying goes. 36 1N4454s - replaced! 🙂